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GREENHOUSES

THEIR CONSTRUCTION and EQUIPMENT

W. J. WRIGHT,

Director, New York State School of Agriculture
at Alfred University. Formerly Assist-
ant Professor of Horticulture at the
Pennsylvania State College

ILLUSTRATED

NEW YORK

ORANGE JUDD COMPANY

LONDON

KEGAN PAUL, TRENCH, TRUBNER & CO., Limited

19 17

Entered at Stationers' Hall
Londp»^ Ei^Jatid

Printed in U. S, A.

TO MY FATHER

IN WHOSE FLUE-HEATED, SHED ROOF PROPAGATING

HOUSE I FIRST LEARNED TO LOVE THE

SMELL OF THE SOIL

PREFACE

In 1912 the author was asked to present a
paper before the National Vegetable Grow-
ers' Association on the construction and
equipment of greenhouses, with special refer-
ence to the vegetable forcing industry. Much
of the data given in this paper had been
hitherto unavailable and was based on an
extensive personal survey of greenhouse
owners and operators, supplemented by per-
sonal experience and observation. So great
has been the demand for this data that at the
request of the Orange Judd Company, the
author has undertaken to incorporate it in
book form. The present volume attempts
a more thorough discussion of the subject
than could be given in a single paper. It
is based upon a series of lectures given be-
fore the author's classes.

This is the second book, dealing exclu-
sively with this subject, which has been pub-
lished in the United States. The former,
written by Prof. L. R. Taft and published by

vi PREFACE

the Orange Judd Company in 1893, has been
the standard and only work devoted entirely
to greenhouse construction as adapted to
American conditions. To this and to Pro-
fessor Taft the author of the present volume
is deeply indebted. It is not intended that
this second book shall supersede the former
but that it shall supplement it and emphasize
present-day features. Probably in no line of
horticulture has so great progress been made
in the past quarter of a century as in floricul-
ture and vegetable forcing. The develop-
ment of the forcing house has been no less
rapid.

No attempt has been made to discuss the
question of greenhouse construction from the
standpoint of the manufacturer, although
due credit must be given to the energy and
ingenuity v^hich he has displayed in meeting
the rapidly changing conditions and in the
excellence of present-day construction. It
is probably not too much to say, that the
development of the flower and vegetable
forcing industry has been largely dependent
upon the improvement which has been made
in the manufacture of greenhouse material
and equipment.

The real purpose of the book is to pre-

PREFACE vii

sent to the reader such information con-
cerning the location, adaptation, general con-
struction and equipment of greenhouses as
will enable him to decide upon the type of
house best adapted to his special needs; to
supervise or assist if need be in its construc-
tion or erection; to arrive at some conclu-
sion as to the equipment most likely to ren-
der the service required, and the probable
cost. A special effort has been made to make
the volume of service to the present owner
of a greenhouse and to those who may con-
template building, whether it be a small
private house or a large commercial range.
The arrangement of topics is made with
reference to a pedagogical system which
it is. hoped will be of service to the teacher
and student.

It is practically impossible to give in-
dividual credit for all the sources drawn up-
on in the preparation -of this volume. Spec-
ial mention should be made, however, of the
assistance given by the manufacturers of
greenhouse building material and for the
many excellent illustrations which they have
furnished. When practicable, the source of
these illustrations is given. Free use has
also been made of bulletins of the various

viii PREFACE

Experiment Stations and of the United
States Department of Agriculture.

The book is offered with a full conscious-
ness of its shortcomings, but with the hope
that it may be of some definite service and
that it may serve as a focusing point for
criticisms and suggestions, out of which
may be born a fuller knowledge through the
experience and observation of its readers.

W. J. Wright.
New York State
School of Agriculture, 1917,
Alfred, New York.

CONTENTS

CHAPTER' I
A General Survey 1-0

Classes of sash-beds — Classes of green-
houses— Evolution of the greenhouse.

CHAPTER H
Sash-bed Construction .... 10-34

Hotbeds, location of, sash, pit, manure for —
Coldframes — Cold or storage pits — Forcing
boxes — Gable roof sash-beds — IMa^ts and
shutters — Care of sash-bed materials.

CHAPTER III
Greenhouse Proper — General Con-
siderations 35-49

Location — Arrangement — Size of houses —
Pitch of roof — Measuring the pitch — Length
of rafters.

CHAPTER IV
Greenhouse Architecture . . . 50-62

Lean-to or shed-roof houses — Even-span or
span-roof houses — Uneven span houses —
Ridge-and-furrow houses — ^Side hill houses
— Curved roof houses — Curved cave houses
— Circular houses.

CHAPTER \^
Structural Material 63-79

Glazing sill — Eave plate — Gutter — Glazing
bars — Side posts — Sash bars — Gable bars —
Drip gutters — Purlins — Ridge — Kinds of
wood used — Framing.

X CONTENTS

CHAPTER VI
Framework, Methods of Erecting . . 80-96

Cardinal virtues of a good greenhouse frame-
work— Foundations and walls — Wood-frame
houses — Semi-iron *frame houses — All-metal
frame houses.

CHAPTER Vn

Glazing and Painting 97-120

Greenhouse glazing an art — Glass to use —
Size of glass — Lapped glazing — Butted glaz-
ing— Putty — Setting the glass — How to esti-
mate putty — Glazing points — Precautions —
Liquid putty — Substitutes for glass — Kind of
paint — Amount of paint required — Shading
— Glazing ladder.

CHAPTER VHI
Ventilation and Ventilating

Machinery 121-141

Systems of greenhouse ventilation — Side
ventilation — Overhead ventilation — ^Size of
ventilators — Hanging ventilator sash — Venti-
lator operating machinery — Shafting — Shaft
hangers — Gearing — Ventilator arms — Capa-
city of ventilating apparatus — Sliding shaft
system.

CHAPTER IX
Beds, Benches AND Walks .... 142-357

Advantages and disadvantages of benches —
.Raised beds — Wood benches — Iron frame
benches — Concrete benches — Height and
width of benches — Arrangement of benches
and walks — Walks and curbs.

CHAPTER X
Greenhouse Heating 158-166

The principles of greenhouse heatino;. — Heat-
ing with flues — Hot water vs. steam heating
— Combination heating systems — Heating
coils — Cast iron and wrought iron pipes for
heating.

CHAPTER XI
Hot Water Installation .... 167-187

General principles — Formula for determin-
ing velocity of water in heating systems —
Estimating radiation — Amount of pipe re-
quired— Size of flow pipe — Length of coils
— Exp^tnsion tank — Pressure systems.

CONTEXTS xi

CHAPTER XII
Steam Installation 188-199

General principles — Size and length of coils
— Size of supply and return pipes — Valves —
High pressure steam heating — Vacuum and
vapor systems — Arrangement of boilers —
Steam pumps and steam traps.

CHAPTER XIII

Boilers, Fuels and Flues .... 200-225

Essentials of a boiler — Grate surface — Fire
surface — Types of boilers — Cast and wrought
iron boilers — Styles of cast iron boilers —
Styles of wrought iron boilers — Steam and
hot-water boilers — Boilers for burning hard
and soft coal — Under-fed boilers — Self-stok-
ing boilers — Size of chimneys and flues — ■
Arrangement of flues.

CHAPTER XIV
Water Supply and Irrigation . . . 226-241

Amount of water required — Types of pumps
— Capacity of pumps — Power required —
Hydraulic rams — Capacity of rams — Wind-
mills for pumping — Storage tanks — Capacity
of storage tanks — Overhead irrigation —
Sub-irrigation.

CHAPTER XV
Concrete Construction .... 242-256

How concrete is made — Kind of sand re-
quired— Kind of stone or gravel required —
Crushed stone — How materials are propor-
tioned— Directions for mixing — Amount of
water required — Estimating materials —
Forms for walls — Reinforcing — Walks and
floors — Water-proofing — Concrete blocks —
Cost of concrete work.

CHAPTER XVI
Plans and Estimates 257-262

Basis of estimate — Average costs — Detailed
estimates — Information required in obtain-
ing estimates.

LIST OF ILLUSTRATIONS

PAGE

Conservatories, New» York Botanical Gardens

Frontispiece

1 Hotbed in operation ...... 10

2 Standard hotbed sash ...... 12

3 Double-glass sash ...... 15

4 Plan" for permanent hotbed . . . .19

5 Permanent hotbed of concrete with cast-iron sills 19

6 Plan for temporary hotbed . . . . .20

7 Type of hotbed used when a large amount of

heat is required ...... 20

8 Usual type of concrete hotbed . . . .21

9 Hotbed arranged for heating by flues . . 23

10 A good type of coldframe . . . . .24

11 Coldframe with sash removed . . . .25

12 A cold or storage-pit . . . . . .26

13 Sash-bed attached to basement of dwelling . 28

14 Types of forcing boxes or plant forcers . . 29

15 Forcing boxes in use on a commercial scale . 29

16 Gable-roof sash-bed heated by manure . . 30

17 Rye straw mats rolled for storage . . .31

18 Hotbed covered with mat and shutter . . .32

19 Private range of C. E. Chapman, Oakdale, N. J. . 37

20 Ground plan of range shown in Fig. 19 . .38

21 Commercial range of Hoerber Bros., DesPlaines,

111 . .39

22 Ground plan of range shown in Fig. 21 . .40

23 Part of vegetable forcing range of Searls Bros.,

Toledo, Ohio . . . ... .41

24 Diagram showing method of mea^suring pitch of

roof ^ . . .42

25 Commercial range of C. FI. Metcalfe, Milford,

Mass " . . .43

26 Diagram showing how heat and light rays are

lost by reflection . . . . . .44

26a Diagram showing pitch of roof necessary to pre-
sent an angle of 90 degrees to fhe sun's rays
in winter . . . . ... . .45

27 An uneven span greenhouse . . . .53

28 Uneven span, side-hill vegetable house . . 55

xiii

xiv LIST OF ILLUSTRATIONS

PAGE

29 Ridge-and-furrow houses wrecked by a storm . 57

30 Diagram showing that the same amount of roof

is required for several small, connected houses

as for one large house covering the same area 58

31 Diagram of side-hill range . . . . .60

32 Curved-eave and circular types of construction . 61

33 Two methods of framing a semi-iron frame

greenhouse ....... 64

34 Types of sills 65

35 Types of eave plates . . . . ,. .66

36 Types of gutters . . . . . .67

37 Type of gutter for curved-eave houses . . 68

38 Cross section of corner bar . . , .68

39 Types of wood sash bars . . . . .70

40 Two types of patented metal sash bars . . 71

41 King ''Channel Bars" 72

42 "U-Bar" type of sash bar 72

43 Gable rafter 73

44 Combination eave plate and gutter . . .73

45 Pipe strap for fastening sash bars to purlins . 75

46 "Pecky" cypress ...... 77

47 The concentric system of construction . . 78

48 A,^type of all-metal flat rafter construction . 81

49 Plan for an all-wood frame greenhouse . . 85

50 Two methods of framing a semi-iron frame

house ........ 89

51 Structural steel post with board wall . . .90

52 Section of truss-trame greenhouse . . .91

53 Section of combination truss-frame greenhouse 92

54 Method of erecting a large combination truss-

frame greenhouse . . . . . .93

55 Side view of house shown in Fig. 54 . . .95

56 A method of erecting small all-metal frame

houses ........ 96

57 Lapped glazing ....... 102

58 Putty knife . 104

59 Machine for distributing putty .... 104

60 A. window glazing; B, greenhouse glazing . . 105

61 Putty bulb . _ 108

62 Types of glazing points ..... 109

63 Glazing with double pointed glazing points . 110

64 Glazing with single glazing points . . . Ill

65 Glazing ladder used in glazing and painting . 120

66 Greenhouse showing A. side ventilators; B, over-

head or roof ventilators ..... 123

67 Method of under-bench ventilation . - . 125

68 Two methods of hanging ventilator sash . . 127

LIST OF ILLUSTRATIONS xv

PAGE

69 Malleable iron shaft coupling .... 129

70 Shaft hangers . . . . ' . . .130

71 Open column ventilator gearing . . . 131

72 Open column chain operated ventilator gearing 131

73 Closed column ventilator gearing . . . 132

74 Chain system of operating ventilators . . 133

75 Rack-and-pinion system of operating ventilators ,133

76 Ventilators operated by means of rods with uni-

versal joints ....... 135

77 Device for operating side ventilat9rs . . . 136

78 Compact machine for operating side ventilators 137

79 Types of ventilator arms ..... 138

80 Sliding shaft system for operating ventilators . 141

81 Cucumbers growing in ground, no benches used. 143

82 Tomatoes growing in solid raised beds . . 145

83 Solid raised beds of hollow building tile . . 145

84 Two types of wood benches .... 147

85 A type of iron frame bench .... 148

86 Greenhouse bench of concrete .... 150

87 Method of arranging benches in an uneven span

house ........ 153

88 An arrangement of benches in a 30 foot house . 154

89 Another arrangement of benches in a 30 foot

house ........ 155

90 A combination steam and hot water heating

system ........ 162

91 Under bench heating with large cast iron pipes . 165

92 Diagram showing "down hill" and "up hill" sys-

tems of hot water piping . .... 170

93 A type of automatic air valve .... 171

94 A method of piping a medium size house . . 178

95 Diagram showing under-bench method of hot

water piping ....... 179

96 Gasoline engine arranged to circulate hot water

in a greenhouse heating system . . , 180

97 Automatic expansion tank ...... 182

98 A type of mercury "generator" .... 185

99 A corner coil 191

100 A mortise coil 192

101 Reducing valve ....... 195

102 A type of steam return trap .... 199

103 A type of "vertical" or "square" sectional boiler 204

104 End view of "square" sectional boiler showing

fire travel 205

105 Side view of "square" sectional boiler showing

fire travel 206

106 Battery of five cast iron sectional boilers . . 207

xvi LIST OF ILLUSTRATIONS

PAGE

107 A t3-pe of "round" or ''horizoQtal" sectional

boiler 208

108 Corrugated fire box boiler ..... 209

109 Type of tubular boiler much used in greenhouse

heating 210

110 Battery of two marine type boilers used in green-

house heating . . . . . .211

111 Wrought iron boiler without flues . . . 212

112 Sectional view of boiler shown in Fig. Ill . . 213

113 Altitude guage 215

114 Water column and guage ..... 216

115 Steam guage ....... 217

116 Diagram of automatic damper regulator . . 217

117 Asbestos pipe covering ..... 218

118 Boiler equipped for using natural gas . . 219

119 Chimneys should extend above the roofs of ad-

jacent buildings . . . * . . . 224

120 Pumping jack ....... 227

121 Diagram showing installation of auto-pneu-

matic pump ....... 228

122 A simple type of hydraulic ram .... 232

123 Plan for installing a hydraulic ram . . . 233

124 Overhead' irrigation ...... 239

125 A type of nozzle used in overhead irrigation . 240

126 Greenhouse bench arranged for sub-irrigation . 241

127 Proportions of cement, sand and stone required

to form concrete ...... 245

128 Form for a concrete wall ..... 250

129 Method of facing a concrete wall . . . 251

130 Structure of a concrete walk . ' . . . 253

131 A small power m.achine for mixing concrete . 255

GREENHOUSES

CHAPTER I
A GENERAL SURVEY

It is not the purpose of this book to furnish
detailed information concerning the manu-
facture of greenhouse building material, for
the cutting and shaping of the materials is
the work of the mill and the factory. Its
purpose is rather to present such informa-
tion concerning the location, adaptation,
erection and equipment of greenhouses as
will enable the reader to decide upon the type
of house best adapted to his special needs; to
supervise or assist if need be, in its construc-
tion or erection; and to arrive at some con-
clusion as to the equipment most likely to
render the service required.

Greenhouses are the result of an attempt
on the part of man to create conditions favor-
able to the growth of plants in climates or
during seasons naturally unfavorable. They
must, therefore, protect the plants from cold
and storms, allow for an abundance of direct
sunlight, provide for ventilation and in most

2 ■ GREENHOUSES

cases they must be equipped with facihties
for artificial heating.

In a general sense, the term greenhouse re-
fers to those glass structures used for the
growing of plants. They are for the most
part above ground and are house-like in ap-
pearance. There is, however, another gener-
al class of glass structures also used for the
growing of plants but which are low and
often almost wholly under ground. Unfor-
tunately, there is no general term commonly
applied to them as a class, but since it is
common to use in their construction certain
standard-size glass sash, the author ventures
to suggest the term sash-bed as a general
one to include structures of this class; and it
is so used in this book.

CLASSES OF SASH-BEDS*

Hotbeds. — These are low structures, being
almost wholly under ground, but having a
glass roof made up of sash which are of con-
venient size to be lifted off, so that the grow-
er may care for the plants. They are usually
warmed by the heat generated by decaying
vegetable matter, commonly horse manure.

*For details see Chaptef II.

A GENERAL SURVEY 3

Their chief use is for starting plants in early
spring.

Coldframes. — These are similar to hotbeds
but are seldom heated and may therefore be
of more shallow construction, as no pit is
needed to store the manure. Their chief use
is for the growing and protection of young
plants after they have been started in hot-
beds or forcing houses, or for the growing
of plants in late spring after danger of severe
weather has passed.

Coldpits. — These are deep pits chiefly used
for the storing of bulbs and semi-hardy
plants during the winter. They are usually
provided with sash roofs the same as hot-
beds and coldframes, so that light may be ad-
mitted when desired.

CLASSES OF GREEN-HOUSES
Forcing Houses. — These are greenhouses
used for growing or "forcing" plants at other
times than at their natural seasons. Prac-
tically all houses used by commercial florists
and vegetable growers are forcing houses.
Conservatories. — In this class of green-
houses, plants are kept mostly for display.
Often it is not desired that the plants so kept

4 GREENHOUSES

shall grow rapidly, but that they shall merely
live. Often also they house for the most
part such semi-hardy evergreen and other
ornamental plants as may be grown outside
during the summer. Such houses are com-
mon in parks and private estates. They are
usually ornamental in character, often with
curved roofs, and present a lively contrast to
the severe simplicity of the commercial forc-
ing houses.

Propagating Houses. — These houses are
devoted principally to the propagation or
starting of plants, especially those grown
from cuttings. As cuttings require little
direct sunlight, these houses are often erected
on the shady (north) side of other green-
houses or in out-of-the-way places. They
should be equipped with benches, underneath
which the heating pipes should be placed to
furnish "bottom heat.''

The term hothouse, as commonly used, is
a general term synonymous wnth greenhouse,
and may be applied to any of the above
classes.

The term stove house is an old one, orio:in-
ally applied to any greenhouse used for tropi-

A GENERAL SURVEY 6

cal plants and thus of necessity kept at a high
temperature. The use of this term is more
common in England than in this country.

A RANGE of greenhouses implies several
houses more or less closely connected and
under one management. The individual
houses may be of any one of the classes men-
tioned above or a combination of two or more
classes. Such houses are often spoken of as

a RANGE OF GLASS.

A range of forcing houses is sometimes
spoken of as a battery, and a range of sash-
beds as a NEST.

EVOLUTION OF THE GREENHOUSE
It is said that the Romans, even before the
time of Christ, possessed some knowledge of
the forcing of fruits and vegetables, and util-
ized for this purpose pits covered with slabs
of a transparent mineral. Heat was supplied
by fermenting manure, and occasionally by
furnaces of masonry in which a slow fire of
wood or dried manure was kept burning.
How successful they were we do not know;
but it seems certain that if any degree of
perfection was obtained, it was because of
the skill of the gardener rather than because
of any special merit of the forcing pits.

6 GREENHOUSES

Forcing houses seem to have had their
origin in an attempt to grow in the northern
countries of Europe fruits such as the orange
and grape, which were grown to such perfec-
tion in the countries to the south. Thus in
England the grape vine is hardy, but the
summers are too cool and the seasons too
short to ripen the fruit to perfection. This
led to the training of the vines on the south
side of buildings and walls that they might
receive more fully the light and heat of the
sun. Later there was conceived the possibil-
ity of still further protecting them by the use
of glass sash leaned against the wall. From
this it was an easy step to the building of
a rather permanent framework close to the
walls, on which glass sash were placed when
required, forming a closed house. Sometimes
the walls were made hollow and slow fires
built within them to give additional heat.
Finally the idea of heating the air instead of
the walls on which the vines were trained
resulted in the building of brick and stone
stoves or fireplaces within the glass enclos-
ures. These houses were never intended for
winter use, but simply to make the summer
and fall conditions similar to those farther
south.

A GENERAL SURVEY 7

The attempt to grow the orange in these
northern chmates presented a different prob-
lem because the trees had to be protected
during the winter. This resulted in the build-
ing of framework structures which were
covered during the winter with wooden shut-
ters and heated by means of a stone fireplace.
There was little or no glass used, but the
shutters were removed during the summer,
leaving nothing but the framework to ob-
struct the light and heat of the sun. A house
of this description, built early in the 17th
century by one Solomon de Gaus at Heidel-
berg, Germany, is said to have been 32 feet
wide and some 400 feet long, and to have
sheltered 400 orange trees.

The next decisive step in the evolution of
the modern greenhouse seems to have been a
combination of the two preceding types, de-
signed for the growing of plants during the
winter. They were permanent buildings
having opaque roofs and high side walls,
resembling dwelling houses, except that they
were well supplied with side windows.

At this time it was thought necessary to
have opaque roofs to prevent freezing, and it
became common to have a second story,
which was used as a dwelling by the garden-

8 GREENHOUSES

er, in order to prevent the heat from escaping
or the frost from "entering" through the
roof. It was not until the early part of the
1 8th century that glass roofs were found to
be practicable, and they were even then slow
in coming into use.

The first greenhouses in this country sug-
gestive of the modern forcing house came in-
to existence toward the close of the i8th cen-
tury. For the most part they were narrow
houses of the shed-roof type, having a solid
wall to the north and a glass roof sloping to
the south. ^ They were warmed by flues,
usually of brick, passing through the entire
length of the house, and connected with a
brick fireplace at one end and a chimney at
the other. Following this, there came in
rapid succession, improvements in form and
methods of construction and especially in
heating, both steam and hot water, being
used early in the 19th century.

The real progress in greenhouse construc-
tion in this country came with the industrial
development of the country after the Civil
War. The United States census reports show
that there was but one commercial green-
house prior to 1800; only three prior to 1820,

{

A GENERAL SURVEY 9

and only 178 in i860. It was not until 1890
that greenhouses had assumed sufficient im-
portance to secure a place in the census re-
ports. At that time there were 4,659 estab-
lishments covering 38,823,247 square feet,
valued at $38,355,722.

The following table shows the total num-
ber of square feet under glass in the United
States and ten principal states, as shown in
the census reports for 1910, 1900 and 1890.
The rank of the states has changed material-
ly during the past 30 years.

AREA UNDER GLuVSS IN THE UNITED STATES AND TEN
PRINCIPAL STATES. FROM CENSUS REPORTS

1910 1900 1890

Tot. Glass Greenh'ses Tot. Glass Greenh'ses* Tot. Glass

sq. ft sq. ft. sq. ft. sq. ft. sq. ft.

U.S. 114,665,276 105,165,730 96,230,420 80,544,862 38,823,276

111. 15,950,853 14,380,857 8,744,020 7,318,744 3,236,750

N. Y. 15,066,587 13,878,875 13,635,440 11,412,863 6,947,289

Penn. 13,846,672 12,887,672 11,819,610 9,893,013 6,066,144

N. J. 8,840,511 7,984,752 11,190,250 9,356,283 3,703,554

Ohio 7,583,562 7,091,976 7,970,190 6,471,049 2,785,192

Mass. 7,382,009 6,817,585 8.710,280 7,290,504 2,717,946

Cal. 5,087,132 4,422,423 1,572,480 1.316,165

Mich. 4,122,099 3.922,772 2.593,230 2,170,233 1,293,44.>

Mo. 2,812,221 2,545,138 3,126,400 2,616,786 1,240.00?

Iowa 2,183,182 1,870,840 1,436,260 1,202,149

Ky. 1,163.241

Conn. 1,060,920

•Estimated.

CHAPTER II
SASH-BED CONSTRUCTION

HOTBEDS

As stated in the preceding chapter, hot-
beds are low structures almost wholly under-

Fig. 1. — Hotbed in operation

ground, but having a glass roof made up of
sash. They are usually heated by ferment-
ing horse manure placed in the bottom, but
may be heated by brick or tile flues, or by
steam or hot water. Their chief commercial
use in for the starting of early vegetable and
flowering plants. In the home garden they
may be used for growing to maturity in early
spring or late autumn, such semi-hardy and

SASH-BED CONSTRUCTION 11

quick maturing vegetables as radishes and
lettuce, and thus extend the season for sev-
eral weeks or even months. They may also
be used for starting and protecting early in
the season, other slower growing crops such
as melons, which are not transplanted but are
allowed to mature in the beds. A gain of
several weeks may thus be secured in the
time of ripening. Well constructed and pro-
tected hotbeds will withstand a temperature
as low as zero if it is of short duration.

Location. — The location for the hotbed
should be (i) relatively high; (2) well drain-
ed; (3) exposed to the sun throughout the
day; (4) protected from north and north-
west winds; and (5) either comparatively
level, or sloping toward the south or south-
west. For convenience it should be near
some building which may be used as a work-
room, and should be close to a supply of
water. The south side of a building is often
an ideal location, although there is some dan-
ger, if the building be a light colored one,
that the hotbed may become overheated.

Sash. — Standard hotbed sash are 3x6
feet, and from 1% to I'^/s inches thick, the
latter being more durable but heavier to

GREENHOUSES

handle. Since they are subjected to especial-
ly rough usage, they must be well construct-
ed of good material, and must be kept well
painted. Well constructed sash may be se-
cured from any reliable dealer in greenhouse

'f =--rs?-:=:^=----='^s>,£aa„a

1 "'

I'll

Fig. 2, — Standard Hotbed Sash

A, three run sash; B, four run sash; C; Horned sash;

X, iron rod to keep sash from spreading

material. They may be of either cypress
or ced^r and have mortise and tenon joints,
though' the tenons should not extend quite
through the bars, or they will be more likely
to absorb moisture and thus decay rapidly.
All joints should be painted with thick lead
paint and should be put together while the
paint is green. Sash with a light iron rod or
bar across the middle, connecting the side

SASH-BED CONSTRUCTION 13

bars, will usually prove to be more durable,
as the rod prevents the sides from spreading.

Most hotbed sash consist of three rows of
glass so laid that the water will flow length-
wise of the sash. For this purpose i8 panes
of lo X i2-inch glass are required. Sash hav-
ing four rows of glass are not uncommon,
but the extra bar and laps obstruct so much
light that they are less satisfactory, and they
are rapidly going out of use. They require
28 panes of 8 x lo-inch glass. Sash may be
purchased either glazed or unglazed. When
time is plentiful and the workman is handy
with tools, they may be glazed at home at a
considerable saving in cost.

Well made sash may be had, unglazed and
unpainted, at from $1 to $1.25 each. The
same sash glazed and painted cost from $3 to
$3.50 at the factory. The price of glass varies
greatly from year to year, but on the average
will cost from 75 cents to $1 per «ash.
Roughly speaking, the sash, putty and* paint
will cost about $2.25, leaving from 75 cents
to $1.25 for the labor of glazing and painting.
Sash of varying sizes are sometimes seen, but
their use is not advised. It is seldom possible
to replace them as cheaply as when standard
size sash are used.

14 GREENHOUSES

When sash are glazed at home they should
first be primed with a coat of lead paint. On
looking them over it will be observed that
one of the end bars is not so thick as the
other, the upper surface being in line with
the bottoms of the grooves or channels made
to receive the glass. This is the lower end of
the sash and should always be placed toward
the southjs The glazing also begins at this
end. In glazing, the first pane is laid flat, the
bottom of the second lapped over the top of
the first and so on, small brads or glazing
points being placed at the lower end of each
pane and along the sides to hold them in
place. Since the lap obstructs the light it
should be as narrow as possible, an eighth
of an inch being as wide as necessary. In
order to obviate the necessity of cutting the
last glass to keep the laps even, it is well to
lay all the panes for one row on loosely, and
to space them before fastening any. They
should then be puttied the same as ordinary
windows, and thoroughly painted.

A more satisfactory way of setting the
glass is to bed them in putty as described in
Chapter ATI, but this method is rarely used
with hotbed sash. Sometimes the glass are
butted; that is, they are laid flat, end to end,

SASH-BED CONSTRUCTION

instead of lapped. This is rarely satisfactory
for hotbed sash; because (i) the panes are
often not squarely cut and do not fit well, and
(2) the sash have so little pitch or slant when
in use that water is apt to run through be-
tween the panes.

Some makers offer a form of sash known
as ^'horned sash," in which the side bars ex-
tend two or three inches beyond the end bars.
These extensions make convenient handles
for carrying, and it is claimed that a better
joint can be made than when they are cut off
flush with the end bars.

Double-glass Sash, as the name implies,
are constructed with two layers of glass with
an air space of about a half-inch between.
They have certain advantages over single-
glass sash which may be stated as follows :
(i) They give greater protection; (2) they
reduce labor, as it is not necessary to use

Fig. 3. — Double Glass Sash

16 GREENHOUSES

mats as late in the season; (3) In moderate
climates no mats or supplementary protec-
tion IS needed; (4) the plants receive sun-
light during the entire day when mats are
not used, whereas, with single glass sash,
the mats have to be left on until the sun
is well up and then have to be replaced be-
fore sundown.

On the other hand, they have several dis-
advantages: (i) The first cost is often as
much as 50 per cent, greater; (2) they are
heavier to handle; (3) they reduce the
amount of light, especially if the glass be-
comes loosened so that dust accumulates
between the layers ; and (4) some users com-
plain that they are short-lived because moist-
ure collects between the layers and promotes
rapid decay.

The most enthusiastic supporters of these
sash are those who live in climates where
this type of sash never need supplementary
protection, but where it is not safe to leave
single-light sash unprotected. It is but fair
to state, however, that their use is rapidly in-
creasing, even in the north.

Temporary Sash, made of oiled paper or
treated cloth, are sometimes used for special

SASH-BED CONSTRUCTION 17

purposes and give more or less satisfactory
results. Directions for making will be found
in Chapter VII.

The Pit. — As most hotbeds are heated by
fermenting manure, a necessary part is a pit
of some depth in which it may be placed.
This pit may be lined with boards, plank,
brick, stone or concrete, the latter being the
most satisfactory. Cypress, cedar, chestnut
and black locust are the most durable, moder-
ate price woods for this purpose. For data
on concrete construction see Chapter XV.

The depth of the pit is determined by: (i)
The severity of the climate and (2) the kind
of plants to be grown. As more heat is pro-
duced for a longer time from a deep pit of
manure than from a shallow one, it is evident
that in cold climates and for plants requir-
ing considerable heat, such as tomatoes and
peppers, the pit must be deeper than in
warmer climates, or for plants like cabbage
or cauliflower which may be grown at lower
temperatures. For starting early vegetable
plants in late February or early March in
the north, 24 inches of manure will be re-
quired, whereas in milder climates, or later
in the season, 12 to 18 inches will be suffi-

18 GREENHOUSES

cient. The manure will continue to give off
heat for three to six weeks.

The dimensions are determined by the
sash. Since sash are 6 feet long and are con-
structed to slope lengthwise rather than
crosswise, the width of the pit north and
south should be a trifle less than 6 feet over
all. The length is determined by the num-
ber of sash desired. Since they are 3 feet
wide, it should be some multiple of three.
For example : A two-sash bed would be 6 x 6
feet, a three-sash bed 6x9 feet, etc. It is
essential that the pit be well drained either
naturally or artificially. If it is to be used in
early spring, it is made the previous fall,
filled with straw or manure and covered with
boards to keep out rain and snow. When
the bed is to be made this material is re-
moved, leaving an unfrozen pit in which
the new manure will heat more evenly and
be more efficient.

The upper or north side of a permanent
hotbed is preferably 6 or 8 inches higher
than the south side to give the proper
slant to the sash. The north side may be
about 15 inches and the south side about 9
inches above the surface of the soil. The
sides are connected with crossbars placed

SASIi-BED CONSTRUCTION

Fig. 4. — Plan for permanent hotbed

even with the top, 3 feet apart, to serve as
rests for the sash and to keep the frames
from spreading. The sides and ends of the
frame are well banked with fresh manure to
conserve the heat. If the plants are to

Fig. 5. — Permanent hotbed of concrete with cast-iron sills

be grown in flats instead of directly in the
soil, 2 inches of soil over the manure will be
sufficient. If the plants are to be grown in
the soil it should be 4 or 5 inches deep.

GREENHOUSES

Temporary hotbeds are sometimes made
by piling the manure on the surface of the
ground and placing a shallow frame on top.

Ground Leyei

Fig. 6. — Plan for temporary hotbed.

This form is wasteful of manure, and the
settling of the pile is likely to warp the frame
so that the sash will not fit tightly. It is
most often used when a hotbed is needed and
a pit has not been dug the previous fall.

Another method is to dig a pit somewhat
larger than the frame. This is filled with
manure to a little above the ground level.

Fig. 7. — Type of hotbed used when a large amount of heat
is required for a long time

SASH-BED CONSTRUCTION

On top of this is placed a frame. The ad-
vantage of this form of bed is that the frame
settles with the manure, thus keeping the
plants always the same distance from the
glass. They are also warmer on account
of the greater quantity of manure used.

Manure for Heating. — Horse manure is al-
most universally used in hotbeds, the pro-

Fig. 8. — Usual type of concrete hotbed

portion being about two parts solid excre-
ment to one part straw or leaves. Manure
which contains shavings is not satisfactory.
Preparation is made lo or 12 days before the
beds are wanted. The manure must be fresh-
ly made and if not moist is dampened, prefer-
ably with warm, though not hot water.
More than enough manure to fill the pit is
provided, for it will shrink somewhat in vol-

22 GREENHOUSES

ume, and some will be needed to bank the
sides and ends. It is placed in layers in a
pile 4 or 5 feet wide, about 4 feet high and
as long as necessary to contain the required
amount, each layer being lightly tramped as
placed. This is done under cover if possible.
After two or three days, or as soon as the
pile begins to steam, it is re-piled, the outside
of the first pile being placed into the center
of the second to encourage even heating
throughout. The manure is moistened with
warm water if it has become dry. If prop-
erly made a vigorous fermentation will have
set in after two or three days and it is then
ready to be placed in the bed. If not
thoroughly warmed through in three or four
days after the second handling, it is re-piled
again every few days until fermentation is
established. Poor heating qualities may be
the result of: (i) Manure from poorly-fed
horses; (2) cold weather; (3) too wet or too
dry manure; (4) too much litter in the man-
ure and (s) shavings or swamp hay used as
litter instead of straw or leaves.

If a steady heat for several weeks is re-
quired, the manure is placed in the pit in thin
layers and trampled quite solidly, especially

SASH-BED CONSTRUCTlOxN

along the sides and in the corners, keeping it
as level as possible. Unless the hotbed is
made so that the frame settles with tlip
manure it must be filled to within 2 or 3
inches of the top of the south side of the
frame to provide for settling. If it is proper-
ly made, the temperature will soon rise to
120 degrees or more, but will gradually fall,
and when it reaches 90 degrees the seeds
may safely be sown. The temperature may
be determined by plunging a reliable ther-
mometer through the soil into the manure.
When a hotbed is arranged to be heated
by flues, drain or sewer tile is used, and the
flues are connected with a fireplace at one end

Fig. 9. — Hotbed arranged for heating by flues

of the bed and a chimney at the other, so
that the smoke and heat from the fire travel
,the whole length of the bed. Hot water or

GREENHOUSES

steam pipes may be run through these flues
if desired, or they may be placed along the
sides of the frame above the soil.

COLDFRAMES
The forcing house, because of its conveni-
ence, possibility of heat regulation and com-
parative cheapness of operation is rapidly
taking the place of the hotbed in a commer-
cial way in the starting of early plants, but
it is promoting the use of coldframes. These
structures rarely receive artificial heat and

Fig. 10. — A good type of coldframe with angle iron
corners, A.

are used largely for the purpose of growing
and protecting plants during mid or late
spring, after they have been started in the
hotbed or forcing house and until they are
ready to plant in the open. They are, in
reality, simply hotbeds without artificial
heat. When banked with manure and pro-
tected with mats, these frames will protect
tender plants at temperatures of 15 or 20 de-
grees below freezing, if of short duration.

SASH-BED CONSTRUCTION

The best frames are made of cypress and
are joined at the corners by means of angle
irons and bolts so that they may be easily
taken apart for storage.

Fig. 11. — Coldframe with sash removed. The sash rest on
the crosspieces, X.

When large numbers of frames are used in
relatively mild weather, they may be very
cheaply constructed by placing two planks
parallel to each other and 6 feet apart. The
plank on the north side is 12 inches wide
and the one on the south side 6 inches wide.
When the plants are removed the planks may
be taken up and stored, or allowed to re-
main, and crops may be planted between
them.

In mild climates, coldframes may be util-
ized for starting early plants before
danger from frost is over, although it is often

GREENHOUSES

advisable to equip them with steam or hot
water pipes, so that they may be heated in
case of emergency. In the north, cold-
frames are used for wintering violets, pansies
and other semi-hardy plants; and farther
south, for wintering cabbage, cauliflower and
other plants which are started in the fall.

ihelf for growing

Fig 12. — A cold or storage-pit

violets

COLD OR STORAGE PITS

In almost every florist's or vegetable grow-
er's establishment there is need for an out-
of-the-way frost-proof storage, to which light
may be admitted on occasion. Such a stor-

SASH-BED CONSTRUCTION 27

age may be easily constructed by excavating
a pit similar to a hotbed pit, but deeper,
so that the bottom will be well below the
frost line. This must be well drained and
lined with a brick or concrete wall, which
should extend a few inches above the natural
ground level to prevent water running in at
the top, but is banked at the top with soil or
manure. The pit may then be covered with
sash and protected with mats and shutters
described in a succeeding paragraph.

In cold climates the pit is at least 5 feet
deep. In very severe climates a mulch of
manure 6 inches deep placed for a distance
of 4 or 5 feet around the pit before the ground
freezes, will effectually protect it. As the
normal winter temperature of the soil be-
low the frost line is considerably above freez-
ing, coldpits furnish excellent storage for
gladiola, dahlia and similar plants, and also
for bulbs for winter forcing. A row of stor-
age pits and coldframes along the south side
of a greenhouse is of great convenience.
The house must be provided with a gutter, or
the frames set a foot or more away from the
side of the house to guard against breakage

GREENHOUSES

by snow or ice falling from the roof. A pit
may be attached to the south side of a dwell-
ing and connected with the basement. When
the house is heated by a furnace this may be
easily heated with little expense, and be used
for growing vegetables or flowers through-
out the winter.

Fig. 13. — Sash-bed attached to basement of dwelling

SASH-BED CONSTRUCTION

FORCING BOXES

Forcing boxes or plant forcers are small
coldframes with a single pane of glass,
which are used to place over individual plants
started early in the spring. They are used

Fig, 14. — Types of forcing boxes or plant forcers

for protecting tomatoes, eggplants, melons
and other heat-loving plants, and are re-
moved as soon as continuous hot weather
arrives. They are used also for forcing rhu-
barb, asparagus and other vegetables in early
spring, and for perennial flowering plants.

Fig. 15. — Forcing buxcs in U6c on a commercial scale

GREENHOUSES

GABLE ROOF SASH-BEDS

Sometimes hotbeds and coldframes are

made of two rows of sash set so as to form

a gable roof. They have few advantages

and many disadvantages when compared

Fig. 16. — Gable roof sash-bed heated by manure

with those of the ordinary type. A few
years ago it was quite common to find sash-
beds of this kind with a sunken walk under
the ridge in which the workman could stand,
the heat being supplied by decaying manure
the same as in an ordinary hotbed. Such
beds are convenient to operate in planting,
watering and cultivating, especially in cold
weather. They are not a profitable venture
as a rule, as heat can be supplied more cheap-
ly from coal than from manure. When an
investment has been made in a house of this

SASH-BED CONSTRUCTION

type it will be found to be economy to equip
it with an inexpensive hot water system.

MATS AND SHUTTERS

Hotbeds and coldframes, when used in

climates or seasons in which the temperature

is likely to fall much below freezing, must be

provided with supplementary covering's.

Fig. 17. — Rye straw mats rolled for storage

This is especially true when single-light sash
are used.

Rye Straw Mats, are extensively used for
this purpose. They were formerly made by
hand but are now made by machinery and
are fairly reasonable in price. Each mat is

32 GREENHOUSES

designed to cover two sash and should be
6x7 feet to allow for turning over the ends
of the sash to keep out the wind. An ob-
jection to straw mats is their weight, especi-
ally when wet, and also the fact that mice are
likely to work in them while they are stored
during the summer. With careful handling
they will last three or four years.

Fig. 18. — Hot-bed covered with (C) double glass sash;
(B) sash and straw mat; (A) sash, straw mat and

shutter

Burlap and Canvas Mats, which are pad-
ded with waste cotton and quilted, are easier
to handle than straw mats and are somewhat
more durable. Though usually thinner than
straw mats, they give practically as good
protection. They have the added advantage
of requiring less storage space, and are some-

SASH-BED CONSTRUCTION 33

times treated with tar or other material of-
fensive to mice.

Waterproof Mats, made of heavy canvas,
or sometimes of oiled or rubberized fabric,
seem to have but little advantage over com-
mon mats, except on coldpits, w^hen they are
to be used during the entire winter. They
are relatively expensive.

Wooden Shutters, 3x6 feet in size, made
of half-inch lumber, are occasionally used to
place over the mats. Their chief value is in
protecting hotbeds when made very early in
the season, and for coldpits.

Care of Sash-bed Materials. — As hot-
beds, coldframes and the like, are used for on-
ly a few months during the year, they are
likely to be neglected and thus deteriorate
rapidly. When many are used, their proper
care may spell the difference between finan-
cial success and failure.

If movable frames are used, they should
be taken down and stored as soon as the
plants are out. If they are so constructed
that they do not come apart, easily, they
may be piled one above the other, cleaned and
painted.

34 GREENHOUSES

Sash should be cleaned and stacked under
cover. Rain}^ days may be utilized in paint-
ing them and re-glazing where necessary. It
is economy to re-paint sash every season.

Mats must be handled carefully and dried
as soon as possible after they become wet by
hanging them on a line or fence. They must
be thoroughly dry when stored for the sum-
mer and be kept where mice cannot get to
them.

CHAPTER III

THE GREENHOUSE PROPER— GENERAL
CONSIDERATIONS

Location. — Having determined upon the
geographical location, proximity to market
and fuel supply and the investment in land
which the business may be expected to war-
rant, all of which are without the scope of
this discussion, the points next to be con-
sidered in the location of a greenhouse are as
follows: (i) It should be such that the sun-
light will not be obstructed at any time dur-
ing the day. The probability of high build-
ings being erected in the immediate vicinity
should be taken into account. (2) It should
be well drained either naturally or artificially
and be absolutely free of danger from floods.
(3) It should not be exposed to cold, bleak
winds, as they will quickly make their pres-
ence known in excessive fuel bills. A wind
break of evergreen or other trees will be
found very effective in protecting from winds
but it will be several years before the trees
will be large enough to be of much l)enefit.

36 GREENHOUSES

(4) It should be comparatively level, or gent-
ly sloping toward the south or southeast.
Hillsides, if necessary, may be utilized by
building houses of special design to be de-
scribed later. (5) An unfailing supply of
water at a reasonable cost should be assured.
(6) If the houses are to be erected in connec-
tion with other buildings, they should be on
the south side if possible. For most plants
the advantage of direct sunlight during the
whole day cannot be over-estimated. (7)
The possibility of enlarging the range by the
addition of more houses should not be over-
looked.

Arrangement. — The arrangement will de-
pend to some extent on the size of the range
and the purpose for which it is to be used.
If for private use only, convenience may
often be sacrificed for appearance ; but for the
commercial house the first thought in ar-
rangement is for economy in operation.

For a commercial house the following
points in arrangement should be considered:
(i) The direction in which the houses are to
run. This will be fully discussed in Chapter
IV. (2) The distance between the houses.
This will depend on the size and height of the

GENERAL CONSIDERATIONS

GREENHOUSES

houses and on the value of the land. Little
advantage, except in case of heavy snowfall,
will be gained over the ridge-and-furrow sys-
tem (see Chapter IV) by separating the in-
dividual houses b}^ less than lo or 12 feet. A
fair though not absolute rule is to space the

J LJ— ^; —
^J^ — ' —

P/amis

Fig. 20. — Ground plan of range shown in Fig. 19
—Boiler room is in basement

houses at a distance equal to two-thirds their
height. (3) The workroom should be con-
venient to all houses of the range, yet shade
them as little as possible. (4) Other things
being equal, the boiler room should be at the
lowest part of the range in order to secure
good circulation. When the houses are long
it is usually best to have it near the center,
and to insure circulation by deepening the

GENERAL CONSIDERATTOXS

GREENHOUSES

boiler pit, or in large establishments by the
use of pumps or steam traps which will be
discussed in the chapters on heating.

Size of House. — There is no authentic data
on the comparative efficiency of small and
large houses. The large houses are relative-
ly lighter, but there are other considerations.

-X7f>-

S^f^vKE Building

AND
BOILCR FtooM

14-

-I7f)-

Fig. 22. — Ground plan of range shown in Fig. 21

As a rule the eastern growers favor separate
large, high and wide houses while those of
the Middle West prefer lower and narrower
connected houses. The present tendency is
to build larger houses than formerly. Of
i6o florists and vegetable growers whom the
author has consulted, 148 or 88 per cent, ex-
pressed themselves in favor of houses rang-
ing from 24 to 40 feet in width. These are
undoubtedly the most popular widths at the
present time, the length varying from 100

GENERAL CONSIDERATIONS

4.2

GREENHOUSES

to 500 feet or more. A discussion of the ad-
vantages of high, wide, single houses and of
low, narrow, connected houses is given in
Chapter IV.

Pitch of Roof. — The pitch of a roof means
the degree of slant or the angle of divergence
from the horizontal. The glass of the roof
not only allows the light, heat and chemical

Fig. 24. — The pitch of the roof is measured at A

rays to pass through it, but it also acts to
some extent as a mirror, thus reflecting a
part of the rays. The amount lost by re-
flection is proportional to the angle of in-
cidence. Thus, if the sun's rays fall upon
the roof at right angles, little or none is lost
by reflection; but when they fall at a less

GENERAL CONSIDERATIONS

?co

O 4>

. o

o
U

GREENHOUSES

Fig. 26. — Diagram showing how heat and light are lost

by reflection

angle, the amount reflected increases as the
angle of incidence increases. The amount of
the sun's energy lost by reflection when the
rays strike the roof at various angles is
shown in the following table.

Table showing per cent, of sun's energy lost when the
rays strike the glass at different angles

Angle of ray Loss by reflection

60 degrees 2.7 per cent.

50 "

40 "

30 "

20 "

15 "

10 " ".

3.4

5.7

11.2

22.2

30.0

41.2

It is apparent that the maximum amount
of the sun's energy may be secured by a roof
presenting to its rays an angle of 90 degrees.
It is especially important that the energy

GENERAL CONSIDERATIONS 45

of the sun be conserved during the short days
of winter. At its lowest period the sun rises,
in the latitude of New York, scarcely more
than 25 degrees above the horizon at noon.
In order for the roof to present an angle of
90 degrees to the sun's rays at this season,
it would need to have a pitch of 65 degrees.

Fig. 26a. — Diagram showing pitch of roof necessary to
present an angle of 90 degrees to the sun's rays in winter

Such a roof would be (i) very expensive to
build and maintain, (2) would present too
large an amount of radiating surface for the
space covered and (3) would be too high to
be practical in houses more than 10 or 15
feet wide.

If, however, we reduce the pitch to 35 de-
grees, the sun's rays will strike the roof at
an angle of about 55 degrees which, by refer-
ence to the table, will be seen to incur a loss

46 GREENHOUSES

by reflection of between 2 and 3 per cent, on-
ly. Roofs of this pitch are not difficult to
build, and do not present so large a radi-
ating surface for the area covered as do roofs
having a pitch of 65 degrees. Roofs having
a pitch of less than 26 degrees are seldom
satisfactory because the snow does not clear
from them well and they are likely to leak.
The water of condensation which forms on
the inside of the roof is also likely to drip up-
on the plants when the pitch is less than
about 26 degrees. When the pitch is greater,
the water will usually follow down the glass
to the edge of the house. In even-span houses
(see Chapter IV) the pitch of the roof varies
from 26 to 35 degrees, 26 and 32 being the
most popular. In some specially constructed
houses it is as great as 45 degrees. Most
builders equip houses up to 25 feet in width
with roofs having a pitch of 32 degrees, and
above 25 feet with roofs having a pitch of 26
degrees.

Measuring the Pitch. — The degree of pitch
of any even-span roof may be determined tri-
gonometrically when the width of the house
and the height of the ridge is known or can
be measured. If the house illustrated in

GENERAL CONSIDERATIONS 47

Fig. 24 is 20 feet wide and the ridge is 7 feet
above the eaves, the value of the angle,
known as A, may be found by the following
formula: Tang. A=^ equals Tang. A— -
equals Tang. A=,yoo or A=35 degrees.

Should the house be of uneven span it is
only necessary to measure the distance
corresponding to a (Fig. 24) and apply
the same formula. When this is not con-
venient, a plumb bob may be dropped from
any part of the roof, as at c, and the distance
measured from the roof to the point c^, where
it cuts a horizontal line or straight edge from
the point where the roof joins the wall. This
distance may be substituted for b in the
formula, and the distance from c^ to the in-
tersection of the roof and wall may be sub-
stituted for a. To avoid error the triangle
thus formed should be as large as possible
and care taken to see that the lines are per-
fectly vertical or horizontal, as the case may
be. By referring to the following table the
angles in degrees and minutes formed by
roofs on houses of various widths and heights
of ridge may be quickly found. The figures
in the left-hand column correspond to half
the width of even-span houses or to the dis-
tance represented by a in the above formula.

GREENHOUSES

Table showing angle formed by roofs on houses of
different widths and heights of ridge

One

half

Heigh

t of rid

ge in feet

wi(

1th

inf

eet

o '

O '

32 21

39 48

49 24

. . . •

• • . •

29 44

35 32

40 36

48 49

• • • •

26 33

36 52

41 11

48 32

23 57

29 3

33 5

37 52

4138

26 33

30 58

38 39

4159

24 26

28 36

32 28

36 2

39 17

4213

22 57

26 33

3015

33 41

36 52

39 41

. . . .

24 47

2818

3136

34 42

37 34

. . . .

23 12

26 34

2944

32 44

35 34

. . . .

28 4

3100

33 40

....

24 13

26 32

It is perhaps more often desired to find the
length of rafter necessary to form a roof of
given pitch on a house of given width, than to
determine the pitch of a house already
erected. This may also be solved trigono-
metrically. For example: Suppose it is de-
sired to know the length of rafter necessary
to form a roof with a pitch of 35 degrees on a
house 20 feet wide. If the roof is to be of
even span, as shown in Fig. 24, we will have
a right angle triangle, A B D, the base of
which is known to be half the width of the
house, or 10 feet. If the angle A is to be 35
degrees then: Cosine A=^^ equals .81915= i?.
Transposing, X=-^^or X=i2.2 feet.

GENERAL CONSIDERATIONS 40

This formula is also applicable to an un-
even span roof provided the distance from the
point directly underneath the ridge to either
side of the house is known. For example : In
a 20-foot three-quarter span house, the base
corresponding to a of the triangle A B D in
Fig. 24 is either two-thirds or one-third of
20 feet, according to which side of the roof
we wish to measure.

In the following table will be found the
lengths of rafters required to form roofs of
various angles on houses of different widths.
The figures in the left-hand column corre-
spond to half the width of an even-span house
or the horizontal distance from the eaves to
a point directly underneath, where it is de-
sired to place the ridge.

Table giving length of rafters necessary to form roofs of
various angles on houses of different widths

One ha

Pitch in de

grees

width

26F

30°

32°

34°

35°

40°

45°

of house

in feet

LENGTH OF

RAFTERS IN

FEET

6.67

6.92

7.07

7.23

7.32

7.80

8.48

8.90

9.23

9.44

9.65

9.76

10.70

11.31

11.12

11.54

11.79

12.06

12.20

13.05

14.14

13.35

13.84

14.14

14.46

14.64

15.60

16.96

13.90

14.43

17.73

15.09

15.25

16.33

17.67

16.80

17.32

17.68

18.09

18.30

19.57

21.21

22.44

23.08

23.58

24.12

24.40

26.10

28.28

27.80

28.86

35.46

30.18

30.50

32.66

35.34

CHAPTER IV

GREENHOUSE ARCHITECTURE

Architecturally, the different forms of
greenhouses are named and recognized main-
ly by the style of roof.

Lean-to or Shed-roof Houses. — These are
the simplest forms of greenhouses; likewise
the least expensive and least satisfactory.
There is little excuse for building separate
houses of this type, but they may be made to
serve a useful purpose when erected against
the side of a building or against a steep side
hill. They usually extend east and west,
with the high wall to the north and the roof
sloping toward the south. For commercial
purposes they are of little value, as they ad-
mit light from only one side, and but little
direct sunlight, except for a few hours in the
middle of the day. They may be utilized for
growing ferns and other plants requiring
little direct sunlight, also for starting early
plants, or as grape or peach houses, the vines
or trees being trained against the north wall.

GREENHOUSE ARCHITECTURE 51

Lean-to houses not only have the advant-
age over other types in less first cost, but
also in cost of maintenance. They have less
glass surface in proportion to the area cov-
ered; hence there is less breakage, and for
the same reason they radiate less heat. For
amateur use, especially when they can be
erected against the south side of the dwell-
ing, they may be built and operated at small
cost and will afford much pleasure.

Even-span or Span-roof Houses. — In these
houses, as the name indicates, the sides of
the roof are of equal length. They are
the most popular form, fully 80 per cent, of
all houses of recent construction being of
this type. They are superior to the lean-to
in that they admit light from two sides, and
also because they may be run either north
and south, or east and west, as may be de-
sired. On this point, however, practical
growers disagree, some preferring the east
and west arrangement, others the north and
south. Theoretically, the points in favor of
and against each seem to about counterbal-
ance. They are stated in the following
paragraph.

The north and south arrangement permits

52 GREENHOUSES

direct sunlight to fall on both sides of the
house for an approximately equal time dur-
ing the day, thus giving all the plants in the
house an equal chance. It also permits the
workroom to be placed on the north end,
where it will not shade the house. The
principal disadvantage is that during the
middle of the da}^ when the sun's rays are
most potent, they strike obliquely against
the roof and much heat and light is lost by
reflection. Moreover, a large part is cut off
by the sash bars and rafters.

In the east and west arrangement, the di-
rect sunlight enters from the south side only,
and in the morning and afternoon strikes the
roof obliquely. During the middle of the
day, when it is most effective, it strikes al-
most at right angles, although it is not even-
ly distributed and the plants on the north
side of the house receive much less than
those on the south side. This would seem to
be a serious fault, but in practice is less
serious than in theorv. Of no o-rowers
whom the author consulted on this point,
38 were in favor of the north and south ar-
rangement, 42 were in favor of the east and
west and 30 expressed the opinion that there
is little or no difference.

GREENHOUSE ARCHITECTURE

54 GREENHOUSES

Uneven Span Houses. — The uneven dis-
tribution of light in even-span houses
running east and west early led to the
experiment of cutting off the north one-
fourth, so as to make an uneven or three-
quarter span house. The following advant-
ages are claimed for these houses: (i) They
secure a more even distribution of direct sun-
light to all plants. (2) The north span ad-
mits indirect light which insures better re-
sults than may be secured from a lean-to
house. (3) The heat is more evenly distri-
buted than in a lean-to house. They are
often used in growing roses and other plants
requiring a maximum of light. The con-
struction of uneven span houses has been
varied from time to time, the general ten-
dency being to lower the north wall to ap-
proximately the height of the south wall.
This arrangement insures even better distri-
bution of light and does away with the neces-
sity of elevated benches.

Uneven span houses are sometimes used
for growing lettuce and other vegetables di-
rectly on the ground instead of in benches,
especially on sloping locations. Modern
greenhouses are so much lighter than the
older types that the advantages of the un-

GREENHOUSE ARCHITECTURE

56 GREENHOUSES

even span house in this connection are hard-
ly worth considering. They are much less
commonly built than formerly. Uneven span
houses are sometimes constructed with the
short span to the south with a pitch of 40
degrees or more. This brings the roof more
nearly at right angles to the sun's rays, but
has little or nothing to recommend it.

Ridge-and-Furrow Houses. — A ridge-and
furrow house is in reality simply two or more
houses joined together. They may be even
span or uneven span so long as the side walls
are of equal height. The advantages of this
form of construction may be mentioned as
follows: (i) They are less expensive to build
than separate houses of similar size, on ac-
count of the saving in side walls. (2) Not
only is there a saving in the number of side
walls, but the interior walls may be of cheap
construction or may be left out entirely, the
weight of the roof being supported by posts
alone. (3) Considerable saving is made in la-
bor because easy passage may be had between
houses. (4) They conserve ground space
which is often a considerable item. (5) The
houses in the center are protected from wind
by those on either side and the radiation is

GREENHOUSE ARCHITECTURE

O I

thus reduced. (6) Because there is less ex-
posed wall surface, and because the interior
houses are protected, they require less fuel
than do separate houses.

One of the chief objections to the ridge-
and-furrow system of construction is the dif-

Fig. 29. — Ridge-and-furrow houses wrecked by a storm

ficulty of removing snow from between the
houses in regions subject to heavy snowfall.
Other disadvantages are: (i) The center
houses are shaded more or less, (2) side light
and side ventilation can not be had, and (3)
soil and other materials must be carried into
the house from the end instead of being put in
at side openings. The latter is a serious ob-

GREENHOUSES

jection only when the houses are long and
narrow.

The above remarks refer only to separate
and connected houses of similar sizes. At
the present time there is a difference of opin-
ion as to the advantages of the single wide
and high house over the small and lower

Fig. 30. — Diagram showing that the same amount of
roof is required for several small, connected houses
as for one large house covering the same area if the
pitch is the same. a+b+cH-d+e-f-f=A+B.

houses connected in the ridge-and-furrow
system. Contrary to the prevailing notion,
the same amount of glass is required by each
system if the roofs are of the same slant or
pitch,

The following advantages are claimed for
the large, single houses: (i) They are more
easily kept at an even temperature, (2) venti-
lation may be secured without subjecting the

GREENHOUSE ARCHITECTURE 59

plants to cold drafts, (3) they are lighter, (4)
they are more easily cared for, (5) the light is
more equally distributed over the whole
house, (6) they quickly clear themselves of
snow, (7) they contain a larger volume of
air, and (8) they require fewer ventilators
and less ventilating machinery.

On the other hand the following disadvant-
ages are pointed out: (i) Their great height
makes them a target for storms which in
winter cause a greater radiation of heat, (2)
they are less easily re-painted and re-glazed,
and (3) the first cost is greater.

Notwithstanding these objections, how-
ever, the single house of moderate size (40 to
60 feet in width) seems destined to become
more and more popular.

Curved-roof Houses. — Curved or curvilin-
ear roofs are now seldom seen, except on
conservatories and show houses. Their chief
use is for ornamental effect. They originated
in an attempt to so arrange the glass as to
more perfectly intercept the direct rays of
the sun, but in practice they have proved lit-
tle, if any, superior to the straight roof, and
the expense is considerably greater. They
have never come into general use in a com-

GREENHOUSES

mercial way. Curved-roof houses are made
to use either curved or straight glass.

Side-hill Houses. — Mention has already
heen made of one of the forms of this type
of house. Sometimes a modification of the

^7/////'

Fig. 31. — Diagram of a side-hill range

ridge-and-furrow house is utilized for side
hill construction. Side-hill houses are not
recommended when well drained, level land
may he secured, because of the disadvantage
of working at different levels.

Curved-eave Houses. — The shade caused
by eave plates and gutters, the difficulty of
keeping them in repair and their interference

GREENHOUSE ARCHITECTURE

62 GREENHOUSES

with the clearing from the roof of ice and
snow in winter, has led to the adoption by
several firms, of the curved-eave construc-
tion. For small and medium-sized houses
the increase in light is very noticeable. In
larger houses it is not so apparent. The ex-
pense for glass is somewhat greater on ac-
count of the curved panes required.

Circular Houses. — These belong in a class
with the round barn and octagonal house —
excellent in theory but impractical in use.
Their first cost and the expense in mainten-
ance places them without the range of econ-
omy as commercial houses. As ornamental
houses in parks and private places, and for
the growing of tall tropical plants they have
their place.

CHAPTER V
STRUCTURAL MATERIAL

Practically all the material, whether it be
wood or metal, which goes into the construc-
tion of a modern greenhouse, is milled or
shaped at the factory. It will almost never
pay the prospective builder to attempt to
use material made by any but specialists in
this line of work. There are several such
firms in this country. Greenhouse construc-
tion, then, so far as the individual builder is
concerned, becomes simply a matter of choos-
ing the kind of material he desires to use;
ordering it from a responsible manufacturer
and assembling it or placing it in its proper
position. Most greenhouse construction
firms have certain standard or stock houses
which they ship complete, even including
nails, paint and putty if wanted, at a definite
stated price; and they will erect them if it is
desired. They will also design and l)uild a
house or range of houses to suit any given
condition.

GREENHOUSES

O O - 03 »-.

en c/) -4-1 e

G ^- N (U 4-.

ot;; ^^

tfl S «) ^ rt

•« o ^1 „

to -^ X

XI C ^ t«

o c c ^ ^

u <u ho
, bfiii > c

I. - -^ ^'-^

CO oj r:

b£) <u rt b «

,« en pi aJ (U

STRUCTURAL MATERIAL

On the other hand, there is now such a
variety of structural material to be had that
it is quite possible, and very often desirable,
for the buyer to design a house according to
his own ideas or to fit his own special needs
or location; select and purchase the materials
and erect it with his own help to suit his
special requirements.

In order to do this it is necessary to know
the names and uses of the various members
which go to make up the house. The prin-
cipal ones are shown in Fig. 33 and are de-
scribed in the following paragraphs.

Glazing-sill or Sash-sill. — This sill is bolted
to the top of the wall, usually by bolts set into

Fig. 34. — Types of sills. A, B. C, and D are wood sills;

E is cast-iron

the concrete, heads down, when the wall is
built. It is known as a sash-sill when the
house is equipped with ventilating sash along

GREENHOUSES

the side walls which close down against it;
or as a glazing-sill when no side ventilating
sash are used and the glass is puttied directly
against it. Sills are used at the ends as well
as at the sides of the house. They are of
various sizes and forms, and may be of either
wood or iron. The small sills are now quite
popular. Grooves on the under side of the
wood sills prevent the water from running
back between the sill and the wall which
would thus cause decay.

Eave Plate. — This plate rests upon the side
posts and forms the support for the roof
members. It ma}^ be of either wood or iron.

Fig. 35, — Types of eave plates. A, B, C, and D are
wood; E is a metal plate

Gutter. — When it is desired to collect the
water from the roof, or when houses are con-
nected in the ridge-and-furrow system, it is
necessary to use a gutter instead of an eave

STRUCTURAL MATERIAL

plate. Iron gutters are rapidly displacing
the old-fashioned wood gutters as they last
longer, and because they need not be so large
and hence cast less shade.

Fig. 36. — Types of gutters. A, and D are wood; B, and

C are metal. C is supported by two rows of posts

to allow for a walk directly underneath

When gutters are used, they have a fall of
at least 4 inches for each 100 feet in length.
This is accomplished by gradulally shorten-
ing the posts toward one end of the house.
In other words, the side walls are higher on
one end of the house than they are on the
other. On very long houses the walls are

GREENHOUSES

Fig. 37. — Type of gutter

(a) used on curved-

eave houses

sometimes so construct-
ed that the gutter
slopes from the ends
each way toward the
center and the water
is carried away at
that point. Detached
houses are less com-
monly fitted with gut-
ters than formerly, on
account of their inter-
ference with the clear-
ing of snow. A special
form of gutter is used
on curved-eave houses.

^//x/"-^//-^^;/
</^>./-///^i^[

Glazing Bars. — These are bars which are
spaced along the sides and ends of the house
to which the glass is
fastened. They are
much the same as sash
bars, which will be
described later, except
that they are usually
somewhat smaller and
are not provided with l^^f^-

grooves to
the drip.

conduct

^ , Fig. 38. — Cross section of

Corner bars corner bar

STRUCTURAL MATERIAL 69

serve the same purpose as glazing bars, ex-
cept that they are so milled that they will
take the glass from both the sides and the
ends of the house. One is used at each
corner.

Side Posts. — These posts bear the weight
and side strain of the roof. They may be
of wood, gaspipe, or structural iron or steel.
Their size will depend on the height of the
wall and the width and construction of the
house. Wood posts 4x4 inches, 2 or 2^-
inch gaspipe, or /^ x 3-inch structural iron
or steel are usually considered amply strong
for most houses. The gaspipe and steel
posts are usually set in concrete and mason-
ry. It is best to set the wood posts in the
same manner. Occasionally the structural
steel, posts are bolted to iron sills which cap
a concrete or masonry wall.

Sash Bars. — The sash bars are among the
most important of all the members which go
to make up a greenhouse. They must be
strong enough to carry the weight of the
glass, yet be of such form and size as to
cast the least possible shade. They are
of various forms and sizes. Bars made en-
tirelv of metal are seldom satisfactory for

GREENHOUSES

the following reasons: (i) They are likely to
expand and contract considerably with
changes in temperature, thus loosening and

t ■

£. r. Q. H.

Fig. 39. — Types of wood sash-bars. E, F, and H are used
for butted glazing; G is used for double glazing

often breaking the glass. (2) The extreme
cold to which they are subjected on the out-
side, as compared with the warm tempera-
ture on the inside of the house, has a ten-
dency to cause them to warp and thus break
the glass or cause it to fit poorly. (3) As all
metals are ready conductors of heat, much is
lost by radiation when they are used. (4) In

STRUCTURAL MATERIAL

cold weather they become so cold as to cause
the moisture in the air inside the house to
condense rapidly on them, which results in a
large amount of drip. V^arious types of bars
have been invented in an attempt to over-
come these difficulties.

Fig. 40. — Two types of patented metal sash-bars

Wood sash bars are not good conductors
of heat and condense but little moisture, but
moisture from the glass finds its way to the
sash bars, so that they are usually made
with a groove or furrow on each side, w^hich
conducts the moisture down to the eaves.
The most common size of wood sash bars is
i'>^ X 2>^ inches. Larger bars are used for
special purposes.

GREENHOUSES

■

Fig. 41. — King "channel bars"

Fig. 42. — "U-Bar" type of sash-bar

STRUCTURAL MATERIAL

Gable Bars or
Gable Rafters. —
(jable rafters are
used at the ends of
the roof and are
made so as to re-
ceive both the glass
of the roof and that
of the end of the
house. They should
be large and strong-
enough to give ri-
Fig. 43.-Gable rafter gidity to the gable.

Drip Gutter. — The purpose of the drip

gutter is to

carry away the

water formed

b y condensa-
tion inside the

house, whicli is

conveyed to it

by the sash

bars. The pipes

leading from it

should empty

into a cistern

or sewer con-
nection inside

,i 1 , I'ig. 44. — Combination eave plate

the house, or be .^^ gutter

74 GREENHOUSES

carried out below the frost line. This is neces-
sary to prevent freezing, as the greatest drip

is in the coldest weather. In some forms of
construction where pipe side posts are used,
they are utilized as conductors of the drip
water, but the saving thus accomplished is
usually more than counter-balanced by the
early rusting out of the posts. Gutters are
made of wood, zinc, tin and galvanized iron.

Purlins. — Since sash bars must be small
to minimize the amount of shade, it is evident
that on wide houses they cannot carry the
weight of the glass without support. This is
accomplished by means of purlins. They
run lengthwise of the house, and are them-
selves supported by purlin posts, by purlin
braces, by rafters or by some form of truss
work to be described later.

When ordinary wood sash bars are used
with glass i6 inches wide, the maximum dis-
tance for safety between purlins is not more
than 7 feet. For example: If the sash bars
are more than 7 feet long, one purlin should
be used. If they are more than 14 feet long,
two purlins should be used, and so on. This
distance decreases as the size of the glass in-
creases since there are fewer bars to sustain
the same weight.

STRUCTURAL MATERIAL

Purlins may be of wood, gaspipe or angle
iron. Wood purlins, because of their size
(1^x3 inches), cast so much shade that they
are now little used. Purlins of i>4-inch gas-
pipe are very satisfactory. They are fast-
ened to each sash bar, and are supported by
posts or braces every 8 feet along their

Fig. 45. — Pipe-strap for fastening sash-bars to purlins

length. A very satisfactory means of fast-
ening them to the sash bars is by means of a
U-shaped pipe-strap. This is placed under
the purlin and fastened to the sash bars by
means of screws.

Ridge. — The ridge furnishes a means of
fastening the upper ends of the sash bars and
also serves as a support for the ventilators.

76 GREENHOUSES

It is milled from a 2 x 4, or a 2 x 6-inch tim-
ber, the size depending on the width of the
house. The form varies according to the
method of attaching the ventilators. (See
Chapter VIII).

Ventilators. — These are fully discussed in
Chapter VIII.

Ventilator Header. — This is a member up-
on, which the lower side of the ventilator
rests.- It is cut and grooved at the factory
so as to fit over the sash bars and to receive
the edge of the glass of the roof in its lower
side.

Sash Hanging Rail. — When side ventilat-
ing sash are used a special piece is sometimes
placed immediately under the eave plate or
gutter, to which the sash are hinged. This is
known as a sash hanging rail. Sometimes
the sash are hinged directly to the plate or
gutter.

Weather Strip. — Because of their construc-
tion and the method of hanging, the roof
ventilating sash do not fit down tightly upon
the sash bars but leave wedge-shaped open-
ings. These are closed by pieces known as
weather strips.

STRUCTURAL MATERIAL 77

Rafters. — Their use is now confined al-
most wholly to all-metal frame houses which
are discussed in Chapter VI.

KINDS OF WOOD

Three kinds of wood are now being used
in greenhouse construction : Cypress, cedar
and California redwood. Of these the first
two are preferred on account of the higher

'^^^H^^H^^Hk

Fig. 46. — "Pecky" cypress

cost of redwood. There is little difference
in the durability of cypress and cedar. If
well framed, and if thoroughly painted when
erected and at least once in two years there-
after, either will last a lifetime.

Pecky cypress is the heartwood from old
trees. It is full of holes or "pecks" and is
often too "shaky'' for sash bars and other
small members, but it is one of the most dur-
able woods known. It is used chiefly for
benches, and in other places where ordinary
lum])er decays rapidly and where great
strens^th is not needed.

GREENHOUSES
FRAMING '

The woodwork of a greenhouse always be-
gins to decay at the joints. For this reason
particular attention is paid to the framing.
All joints are made to fit closely, and before
putting together each piece should be primed
with a thin coat of lead paint. The joints

Fig. 47. — The concentric system of construction

are then given a heavy coating of thick white
lead and put together while the paint is still

green.

In buying greenhouse material it is al-
ways well to buy all the woodwork from one
firm and to give the concern a careful de-
scription of the house, together with a draw-
ing showing the width, height and length of
the house, the pitch of the roof, size of glass
to be used, etc. The firm will then send the

STRUCTURAL MATERIAL 79

woodwork (if it is so directed) cut so that
it may be fitted together with but Httle
trouble. It should be specified, however,
that it be well seasoned and not warped.
Warped millwork, especially sash bars and
glazing bars, are exceedingly difiicult to put
in proper position.

Some factories now build their eave plates
and sash bars on the concentric principle,
which does away with the necessity of cut-
ting the ends of sash bars differently for
roofs of diiTerent angles.

CHAPTER VI
FRAMEWORK— METHODS OF ERECTING

The two cardinal virtues of a good green-
house framework are these : It must be strong
and Hght, and it must cast but little shade.
The greatest advance in greenhouse con-
struction in the last quarter of a century has
been in the framework. The old houses with
their high, solid walls and heavy woodwork
are dingy and dark, when compared with the
modern house, 90 per cent, of which is glass,
with little or no solid wall above ground. The
framework of these houses casts but a frac-
tion of the shadow produced by the old-style
frame, yet it is so perfectly rigid against
storms and snow that the large panes of glass
are seldom broken or even loosened in their
setting.

Three general classes of framework are
used: (i) Wood frame, in which all members,
including the posts, are of wood; (2) semi-
iron frame, in which the posts, purlins and
purlin posts are of pipe or structural iron,

FRAMEWORK

bi)
U

■^

r-i

f—

-!-•

(/)

( ;

-i->

<-t-l
u

t£

'■/

—rf

•.

(/)

-^-*

l_l

»-— 1

., y

82 GREENHOUSES

and (3) all-iron or all-steel frame. In wood
and semi-iron construction, rafters are sel-
dom used, the sash bars performing this func-
tion as well as their own. These forms have
the advantage of being somewhat cheaper
than the all-metal frame construction, and
have the additional advantage that the ma-
terial may be cut and fitted on the job by any
experienced workman.

Wood frame houses cast more shade than
semi-iron, and are less durable, especially the
posts. Semi-iron houses are very durable,
and for houses of medium width, are very
satisfactory. Probably more houses of this
type have been built during the past ten years
than of all others, though the all-metal frame
house is now gaining in favor. This is
especially true in the East, where large
houses are coming into vogue.

The all-metal frames are cut and fitted at
the factory and are then shipped, knocked
down, to the place of erection. Most styles
of all-metal frames have rafters, which are
bolted to the side posts by means of gusset
plates to form bents. The bents are then
placed in position and secured there by stays
and purlins. Upon this framework are then
bolted the wood sash bars and glazing

FRAMEWORK 83

bars. Metal sash bars, as before mentioned,
seldom prove satisfactory. The framework
of such houses is practically indestructible,
and when the woodwork decays it can be re-
placed upon the old framework.

Usually the weakest part of a greenhouse
is the gable. It should be well framed and
securely tied to the purlins and other parts
of the framework.

METHODS OF ERECTION

Foundations and Walls. — In the old-style
high, solid wall greenhouse, the wall was a
source of much perplexity, especially the
high north wall of the uneven span house.
In modern houses, however, the solid wall is
seldom higher than the top of the benches,
when benches are used, or only a few inches
above the surface when plants are grown on
the ground. The remaining part of the side-
wall is constructed of posts and glass, thus
giving more light. The chief difficulty with
the high, solid wall was that the extremes of
temperature between the outside and inside
in cold weather caused them to disintegrate
rapidl}'. This was particularly true with
masonrv walls.

8^ GREENHOUSES

Modern greenhouse walls, for commercial
houses, are almost always of concrete and,
being low, give little trouble. Concrete
blocks and hollow building tile are much
used. The chief requisite is that the founda-
tion shall reach below the frost line. The
common practice is to dig a trench 12 or
15 inches wide and 3 feet deep and fill with
coarse concrete to within a few inches of the
surface. A form is then built of lumber .to
the height required and filled with concrete.
When the concrete has "set," the form is
taken away and the sides of the wall plast-
ered with a cement mortar. In wet, springy
soil it is often desirable to lay a row of drain
tile along the outside of the wall arid nearly
to the bottom of the trench, to carry ofT the
water.

Concrete walls are usually much more
satisfactory than either brick or stone. They
should be from 8 to 12 mches thick, according
to their height and the side strain to which
they are subjected. Usually 8 inches is suf-
ficient. In wet soils when the boiler is placed
below the surface, it may be necessary to
waterproof the walls. For data on concrete
construction see Chapter XV.

FRAMEWORK

Wood Frame Houses. — These are quite
satisfactory when a cheap house is wanted
for a comparatively few years. The side
posts, which may be of cedar or cypress, and
3x4 inches in size, are placed 8 feet apart
in holes 3 feet deep, and extend to the height

Fig. 49. — Plan for an all-twood frame greenhouse

decided upon for the side walls. They are
then placed in alignment and the holes
poured full of thin concrete which soon hard-
ens. The end posts are similarly placed, ex-
cept that they extend only to the height of
the boarded-up portion of the wall.

S6 GREENHOUSES

^ The next step is to place the center posts,
which are usually 2 x 3 or 2 x 4 inches in
size. The height of the ridge having
been determined (see Chapter III) these
posts are cut long enough to allow the
lower end to be set in the ground about 2
feet. They are then put in alignment and
embedded in concrete the same as the side
posts. The ridge is then put in place on top
of these center posts, and the eave plate on
top of the side posts, all joints being set in
thick white lead paint.

The sash bars on a house over 12 feet in
width must be supported with purlins, but it
is not necessary to support them with two
extra rows of posts. A perfectly safe and
much more convenient way is to support
them with arms or braces from the center
posts. This saves valuable ground space, and
the arms serve to stiffen the center posts as
well. The length and position of these arms
may be determined by placing a straight edge
from ridge to eave plate in just the position
the sash bars will occupy, and nailing the
arms fast, first allowing for the thick-
ness of the purlin. A good mechanic would
have determined this before the posts were

FRAMEWORK 87

set, and have nailed the arms in place before
raising them. The amateur, however, will
find it best to put them in place after the
posts are up, or at least to put up a trial post
and then make the others after it as a pattern.

The next step is to nail on the purlin, and
then it is ready for the sash bars, which are
spaced carefully so that the distance from
rabbet to rabbet is about one-eight-inch
greater than the width of the glass. This
can best be accomplished by using a board
about one-eight-inch wider than the glass,
and nailing the bars so that the rabbets fit
snugly against it along their whole length.
The board can then be removed and used to
space the next, and so on.

The side and end posts are next boarded
up to the required height, using two layers
of matched lumber with paper between. The
bottom board, at least, must be of best qual-
ity pecky cypress to guard against decay.
Glazing bars may now be fitted along the
sides between the eave plate and the glazing
sill, and between the glazing sill and the
gable rafters. Corner bars are placed at
each corner.

88 GREENHOUSES

It will also be necessary to make a frame
for the door at one end, and to reinforce the
gable glazing bars with 2 x 4-inch scantling.
The house is then ready for glazing, instruc-
tions for which will be found in Chapter VII.

If cypress or cedar lumber is used through-
out, and if kept carefully painted, a house
like the above should last for fifteen or
twenty years. The most vulnerable parts are
the posts, especially the portion where they
enter the cement. They should be painted
regularly once each year at this point. While
these houses do not admit as much light as
either a semi-iron or an all-iron frame they
will give excellent service. A poorly built
all-wood frame house is a constant expense
for maintenance.

Semi-iron Frame Houses. — Two methods
of framing a semi-iron frame house are
shown in Fig. 33. The method shown on the
left requires twice as many purlin posts as
the one on the right. In each case gaspipe
is used. The work of erecting differs but
little from that described for wood frame
houses, except that pipe working tools are
required, and a little more skill is necessary.
An endless variety of fittings may be had

FRAMEWORK

for this style of framing, which makes the
joining of the frame work comparatively
easy.

If it can be procured, genuine wrought-
iron pipe is best used instead of the steel pipe
now commonly sold. Steel pipe rusts out

Fig. 50. — Two methods of framing a semi-iron house
For others, see Fig. 33

much more quickly. In this style of house the
wall is usually of concrete and may be only a
few inches above the surface of the ground,
or any height desired. The side posts which
are usually of 2-inch pipe are put in position
and stayed before the concrete is poured in,
so that when the wall has set they are per-
fectly rigid. Adjustable brackets which fit
on the top of the posts, and to which the
eave plate or gutter is attached, make pos-
sible the correction of trifling variations in
height.

Bolts are set, heads down, in the top of the
wall while it is soft, and project upward 2 or
3 inches. These are used for fastening down

GREENHOUSES

the sill, which is bored to fit over the posts
and bolts and is secured with nuts. No
posts are set in the end walls, but the bolts
are set the same as in the side walls and are
used for the same purpose.
In some cases the posts are
set in the ground and the side
walls are constructed of two
layers of matched lumber.

The purlin posts and other
supports are put in position
much the same as in the wood
frame house, except that in-
stead of being embedded in
concrete, they are sometimes
provided with foot pieces and
rest on small concrete piers.
Split malleable iron castings
may be had in almost every
conceivable form for joining
the frame together. These arc
fastened by bolts and set screws, so that it is
not necessary to thread the pipe. The sash
bars are fastened to the pipe purlins by
means of U-shaped clips or pipe-straps,
which are secured to the bars by means of
screws. Purlins are usually made of one and

Fig. 51. — Struc-
tural steel post
with board
wall

FRAMEWORK 91

a quarter-inch pipe and should be supported
by posts every 8 feet. Purhn posts are usual-
ly of one and a half-inch pipe and braces of
one and a quarter-inch pipe.

A well-built house of this type, if well
cared for, should last a lifetime.

Fig. 52. — Section of truss-frame greenhouse. The frame
is made of gaspipe

Semi-iron frames are also made from struc-
tural iron instead of pipe. They are just as
satisfactory, but are not so easily worked,
and are usually cut and fitted at the factory.

All-metal Frame Houses. — There are three
types of all-metal framework: (i) Those in
which the roof is supported by interior posts,
much the same as in the wood or semi-iron
houses. (2) Those in which the roof is sup-

92 GREENHOUSES

ported by a truss work, thus doing away with
all interior posts (sometimes known as truss-
frame). (3) A combination of the above
forms (known as a combination truss-frame)
is used in houses so wide as to make the
truss-frame impractical. This is commonly
used in houses over 40 feet in width.

Fig. 53. — Section of combination truss-frame green-
house, 172 feet wide

As has already been mentioned, all-metal
frame houses usually have wood sash bars
and glazing bars, but they are not considered
as parts of the framework. In these houses
the completed framework is entirely of metal,
the wooden members being fastened to the
frame with bolts or screws and serving only
to hold the glass in place.

In many all-metal frame houses, especially
when the roof is supported by inside posts, it
is common to bolt an iron or steel sill to the
wall and then bolt the side posts to this sill.

A method of erecting a modern combina-
tion-truss frame house, 73 feet wide and

FRAMEWORK

94 GREENHOUSES

nearly 30 feet high, to the ridge, is shown in
Fig. 54. This work was done entirely by
the owners and their ordinary help, without
any expert superintendence and at a material
saving in cost.

The method was comparatively simple.
The material was first carefully distributed
on the site selected, and a trench dug for
the foundation. The gable trusses were
then bolted together, while another gang of
men began setting and guying the side posts.
The trench was then filled with concrete,
making the side posts rigid. Next the in-
terior posts were put in place.

The first step in putting up the rafters
was to fasten the lower ends to the tops of the
side posts loosely, so that they would move
easily, and then raise the other end into place
by means of a pair of "shears,'' made of two
pieces of 2 x 4-inch scantling. When these
had been securely bolted in place, the gable
truss, which had been previously assembled,
was swung into place by means of a block
and tackle, working from a boom. All
that remained was to insert and tighten the
bolts, put the purlins in place and move on
to the next bent. The author was told by
the owners of this house that it was erected

FRAMEWORK

GREENHOUSES

with greater ease than any semi-iron house
they had ever built. ,

Fig. 56. — A method of
erecting small all-metal
frame houses

Structural steel is most largely used in
truss-frame houses though gaspipe is now
quite popular. It is claimed for gaspipe that
it costs less than structural steel and that it
casts less shade. Some objection has been
urged against houses constructed of gaspipe
on account of a lack of rigidity, but as now
constructed they give very satisfactory serv-
ice. Houses of this type are regularly sup-
plied by manufacturers up to 54 feet in width,
without center supporting posts. It is prob-
ably safest to have two rows of supporting
posts in houses more than 40 feet in width.

CHAPTER VII

GLAZING AND PAINTING

Greenhouse glazing is an art in itself.
Most construction firms employ professional
glazers. It is, however, an art that may be
readily acquired. Many owners do their
own glazing when occasion requires, or have
it done by their ordinary help. The method
of glazing greenhouse roofs is not the same
as that used in glazing window sash. When
glazers from glazers' shops or hardware
stores are employed, precaution should be
taken to see that they understand the differ-
ence.

Glass. — The glass commonly used in
greenhouse glazing is clear, white, sheet or
window-glass of either A or B grade. Glass
with a pronounced green or bluish cast is to
be avoided, as it obstructs a large part of the
heat, light and chemical energy of the sun's
rays.

Clear, white window-glass ordinarily ab-
sorbs about 30 per cent, of these rays ; green,

98 GREENHOUSES

from 40 to 50 per cent.; and blue, from 50
to 80 per cent.

Glass known as A, or first grade, is blown

from the top of the retort and is of bet-
ter quality than the B, or second grade,
which may contain some foreign matter or
settlings. Some of the less regular panes
from the first blowing and those containing
small air bubbles are also placed in the B
grade. When it is essential that the great-
est possible amount of light be had and tight
glazing is necessary, A grade is used.

In most commercial constructions B grade
will give satisfactory results. Poorer grades
are not satisfactory for greenhouse work.
The cost of B grade is about 85 per cent, of
the price of A grade. Both A and B grades
may be had in two weights or thicknesses,
known as single-thick and double-thick.
Single-thick runs about 12 panes to the inch
and weighs from 19 to 21 ounces per square
foot. Double-thick runs about 8 panes to
the inch and weighs from 26 to 29 ounces
per square foot. Double-thick is almost
always used when the panes are more than
8 X 10 inches in size. It obstructs but little
more light and is much more durable,
especially against hail.

GLAZING AND PAINTING 99

The price of single-thick is from 60 to 70
per cent, of the cost of double-thick. Amer-
ican window-glass is the best that can be
procured. The price varies greatly from year
to year, probably more than does the price
of any other standard building material.

American-made glass is packed in boxes of
about 50 square feet each. Foreign glass
comes in boxes of approximately 100 square
feet each. The number of lights per box of
the various sizes of American-made glass is
shown in the following table:

LIGHTS PER BOX ACCORDING TO SIZE

Lights

ights

Size

per box

Size

:r box

7x 9

114

14x16

8x10

14x18

8x12

16x20

10x12

16x24

10x14

18x18

12x12

18x20

20x14

18x24

12x16

20x20

14x14

20x24

Plate elass is seldom used in commercial

greenhouses, as its cost is prohibitive. It is
but little better than A grade window-glass
for this purpose. In conservatories where
strength is more important than transpar-
ency, fluted or corrugated glass, or glass in-

100 GREENHOUSES

to which wire netting has been blown is
sometimes used. Ground or frosted glass is
occasionally used in palm-houses or ferneries,
where a soft, subdued light is desired. This
effect is more commonly obtained by paint-
ing or whitewashing the clear glass and vary-
ing the thickness of the coating according to
the season of the year.

Size of Glass. — The size of the glass varies
according to the purpose for which the house
is to be used, and the taste and personal pref-
erence of the owner. Where extreme light-
ness is wanted, large panes are used thus
diminishing the number of sash bars. There
is, however, a practical limit to the size. Glass
increases rapidly in price as the size in-
creases, and the large panes break more
easily. Moreover, the size of the sash bars
must be increased to carry the extra weight,
and every increase in their size means more
shade.

Of 136 practical growers consulted on this
point, 108, or. nearly 80 per cent., favored
either 16 x 20 or 16 x 24-inch glass with the
longer edge parallel to the sash bar. That
is, the great majority preferred to have the
sash bars spaced about 16 inches apart.

GLAZING AND PAINTING 101

About 3 per cent, favored i6 x 20-inch glass
with the shorter edge parallel to the sash
bars, the bars in this case being 20 inches
apart. Glass 16 x 20 inches is undoubtedly
the most popular size.

Methods of Glazing. — Practically all
methods of glazing make use of putty to seal
the glass in place and to form an air and
water-tight joint. An exception is made
when some forms of metal bars are used.
With these, felt, candle wicking or some
similar material is usually employed, and the
glass is pressed firmly against it and kept in
place by bolts or clamps. Sometimes a lead
facing is used and the glass is clamped
against this facing.

The great majority of houses are con-
structed with wood sash bars or bars having
wood cores with which putty is supposed to
be used. With these there are two common
methods of setting the glass. It may be
lapped or butted.

Lapped Glazing. — In lapped glazing the
lowermost panes in each run are laid flat
against the bottom of the grooves in the
sash bar. Each succeeding pane is then laid
so that its lower edge laps over the upper

102 GREENHOUSES

edge of the pane below it, in much the same
way that shingles are lapped, except that the
lap is much narrower. From one-eighth to
three-eighth inches are allowed for lapping,
the width of the lap depending somewhat on
the size of the glass and the rigidity of the
house and roof. It should be as narrow as
possible, for little light passes through the
lapped part of the roof.

Fig. 57. — Lapped glazing

Butted Glazing.— In butted glazing all
panes lie flat against the bottom of the
grooves in the sash bars, and the lower edge
of each glass rests directly against the up-
per edge of the one below. This form of
glazing eliminates the lap, but it is more dif-
ficult to secure a tight roof than when
the glass is lapped. Roofs having a pitch
of less than 30 degrees are likely to leak badly
when the glass is butted.

In this form of glazing the putty is some-
times omitted, and the glass is held in place
by wood caps which fit over the rabbets.
When it is desired to make an especially tight'

GLAZING AND PAINTING 103

roof, the upper and lower edges of the panes
are sometimes dipped in a shallow tray con-
taining thick paint. They are laid while the
paint is soft, and in hardening this forms a
tight, waterproof joint. Zinc glazing strips,
bent in the form of a letter Z were at one
time quite extensively used between the
panes to make a tight joint. They are still
used to some extent between the panes on
side and end walls.

Several advantages are claimed for butted
glazing: (i) Less glass is likely to be broken
by accidents, for if only one pane is hit, it
only will be broken; while if the panes are
lapped, the one immediately below is often
cracked. (2) Less glass is broken by the ac-
tion of frosts, as there are no laps in which
moisture can collect and freeze. (3) The
roof is lighter, as there are no laps to ob-
struct the sunlight.

The chief disadvantage, aside from leak-
age, is the difficulty in repairing the roof
when a glass is broken, for the pane must
be cut to fit tightly. In cold, stormy
weather, this is a slow and tedious process.

Butted glazing is much less used than
formerly among practical growers, which is
proof that, in general, it is not so well suited

104

GREENHOUSES

Fig. 58.— Putty knife

for glazing roofs as is
lapped glazing. More than
90 per cent, of the growers
interviewed on this subject
preferred lapped glass
roofs. On side and end
walls, glass is quite com-
monly butted v/ith good
results.

Putty. — Putty is a pli-
able substance used in set-
ting glass. The principal
ingredients are whiting

and linseed oil, and its chief virtues are that

it is easily worked and applied, and that it

does not shrink on

drying, thus making a

water-tight seal. For

greenhouse use, putty

as bought in the gen

era! market should be

mixed with pure white

lead at the rate of one

part of lead to five of

putty. This will stick

to the bars and glass

much better than will Fig. 59.— Machine for dis-

ordinary putty. tributing putty

GLAZING AND PAINTING

105

Putty purchased from dealers in green-
house supplies will not need the addition of
lead. It should be worked as soft as it can
be handled in order that it may be easily
forced into all cracks and crevices. It is
applied with a putty knife or with a putty
machine. The putty machine distributes the
putty rather more rapidly than can be done
by hand, but it is necessary to use a putty
knife in conjunction with it.

Setting the Glass. — The basic difference
between glazing greenhouse roofs and glaz-
ing ordinary window-sash is in the method
of applying the putty. In glazing window-
sash, the putty is placed on the outside. In
greenhouse glazing the putty is placed in the

Fig-. 60. — A, window glazing; B, greenhouse glazing
The putty is shown at a and b

grooves in the bars and the glass is forced
into it. That which oozes up around the
edges is scraped off and used again. By this
method, little putty is exposed to the air, but

106 GREENHOUSES

the glass is sealed by a thin film underneath
and along the sides of each pane. This
method has been developed because experi-
ence has shown that on roofs putty soon
checks and crumbles away when exposed to
the weather as in window glazing.

When glass is lapped, the following meth-
od is used. First, the sash bars should have
been so placed that the space left for the glass
is about one-eighth of an inch wider than the
glass. This provides room for the ''side
putty." (For method of spacing see page
87). Sash bars are usually primed when re-
ceived from the factory. They are given an-
other coat of paint after they are put in
place and are then ready for glazing.

Glazing is started at the bottom of the run.
A line of soft putty is first placed in the rab-
bets and a pane of glass forced firmly into it
until it is imbedded against the bar. A
groove is usually provided in the plate to re-
ceive the lower edge of this glass to prevent
it from sliding down, but if there is no such
groove, three or four brads or glazing points
are driven for the lower edge to rest against.

The excess putty is then removed and the
next glass forced firmly into place, so that
its lower edge laps over and rests firmly on

GLAZING AND PAINTING 107

the top of the first, and its upper edge rests
on the sash bar. This is fastened at the bot-
tom with brads or glazing points to prevent
its sUding down. The remaining panes of
the run may then be placed in the same man-
ner, special care being taken to secure the
uppermost firmly in place with glazing
points. This is necessary because it has no
glass above it to hold it in place, and because
it acts somewhat as a key to keep the others
in position.

It is best to finish each run from bottom
to top before starting on a new run, in order
that the putty may cement into a continuous
mass. On high and wide roofs, however, it
is sometimes advisable to glaze the lower
half of the roof, then move the scaffolding
and glaze the remainder.

How to Estimate Putty. — The amount of
putty necessary to glaze a roof may be esti-
mated as follows: A pound of putty, when
applied by an experienced workman, will
reach about 15 feet along one side of a run
of glass or about 7>^ feet along both sides.
To estimate the amount of putty, therefore,
multiply the length of the run in feet by the
number of runs and divide by yVi. This will
give the number of pounds required. The

108

GREENHOUSES

amount required for the sides and gable may
be found in the same way. An inexperienced
workman will use somewhat more than this
amount as there will be more waste.

In glazing by the ''butted glass'' method,
putty may or may not be used. When it is
used, the method is very similar to that de-
scribed above, except that much
less is required, as the panes are
crowded down to the bottom of
the rabbet along their whole
length instead of only at their
upper end. Sometimes in glazing
by this method no putty is used
until after the glass is laid, and
then a small quantity of liquid
putty is forced down along the
sides of the glass with a putty
Pig. 61. — bulb. Usually when the glass is
Putty bulb ]3|^i|-|-g(^^ j-j^^ h^Ts are surmounted

by wood caps. In this system special care
must be taken to fasten the lower pane, as

the sliding weight of the entire run rests
against it.

Glazing Points. — Glazing points are used
to hold the glass in place. They may be
had in several forms and sizes. A good
glazing point is easily driven, does not split

GLAZIXG AXD PAINTING

109

the wood, offers as little obstruction as pos-
sible to the brush in painting and does not
rust. Small sizes suitable for glazing win-
dow-sash in which the putty is placed on
the outside are too small for greenhouse glaz-
ing. Zinc points of various forms have
been frequently used because of their free-
dom from rust. The triangular point is prob-
ably the most popular of the zinc points, and

Fig. 62L — ^Types of glazing points

is quite commonly used in window glazing.
It is not well suited to greenhouse glazing
on account of the difficulty of fastening the
panes of glass with it so that the}' will not
slide down : x^f.

Probably the most used point in green-
house glazing is the double-pointed staple.
This is easily driven and when galvanized is
not subject to rust. The best form of this
type of staple is bent to an angle in the cen-
ter, so as to fit over and hold the lower edee

110

GREENHOUSES

of the pane from slipping lengthwise, as well
as to hold it down in place.

In lapped glazing only two double points
are used for each pane, that is, one at each

Fig. 63. — Glazing with double glazing points

lower corner. The upper edge is kept in
place by the bottom of the pane above it. Ad-
ditional points are required for the lower-
most and topmost panes in each run, and as
some will be lost and destroyed, it is well to

GLAZING AND PAINTING

111

figure on three points for each pane. An
average of five of the small single points will
be required for each pane.

Fig. 64. — Glazing with single glazing points

Precautions. — All sheet glass is slightly
curved, a condition caused by the process of
manufacture. When seconds or B orade
glass is used, it w^ill sometimes be found that
the panes will be so much curved as to make

112 GREENHOUSES

it difficult to lay a tight roof. If this trouble
is experienced, it will be of advantage to sort
the glass and lay out each run on a smooth
floor, placing the panes having a similar de-
gree of curvature in the same run. By doing
this a tighter and more satisfactory roof can
be laid.

Theoretically, the glass will resist more
pressure if it is placed so that the curve will
be up, that is, so that it will present a convex
surface to the weather. If, on the other
hand, it is placed so as to present a concave
surface to the weather, the water will have
a tendency to flow away from the sash bars
and putty to the center of the runs. In ac-
tual practice, these are relatively unimport-
ant considerations, but all glass in the same
run should have approximately the same
curvature.

Liquid Putty. — This is sometimes used for
sealing cracks in old glazing or in glazing by
the ''butted" method. It may be made as
follows: Take equal parts by measure of
white lead, putty and boiled linseed oil.
First, mix the putty and oil thoroughly and
then add the lead. If it becomes too thick,
thin with turpentine.

GLAZING AND PAINTING 113

Substitutes for Glass. — On hot beds and
coldframes and sometimes on temporary
greenhouses, some transparent material
other than glass is used. The reason for this
is that glass is both expensive and heavy to
handle. The most common substitutes are
cloth and paper treated so as to make them
w^aterproof and semi-transparent. Some-
times a firm but lightweight white cotton
cloth is used with no treatment, but it does
not admit light enough to permit satisfactory
growth of plants for any length of time.

Paper can seldom be used for more than
one year. Cloth may, with care, be used for
several seasons. The best results are secured
by stretching the cloth or paper on rigid
frames or sash on which wires have been
drawn tightly across at frequent intervals to
serve as supports. The author has had good
success by simply painting the cloth or pa-
per, after stretching it over the frames, with
pure, light, boiled linseed oil. Bailey, in the
"Farm and Garden Rule Book," gives the fol-
lowing recipes:

(i) Paste stout, but thin Manilla wrap-
ping-paper on the frames. Dry in a warm
place and then wipe the paper with a damp
sponge to cause it to stretch evenly. Dry

114 GREENHOUSES

again and then apply boiled linseed oil to
both sides of the paper and dry again in a
warm place.

(2) Dissolve iH pounds of soap in a quart
of water ; in another quart dissolve i/^ ounces
of gum arabic and 5 ounces of glue. Mix
the two liquids, warm, and soak the paper,
hanging it up to dry. Used mostly for
paper.

(3) Take 3 pints pure linseed oil, i ounce
sugar of lead, 4 ounces of white resin. Grind,
and mix the sugar of lead in a little oil, then
add the other materials and heat in a kettle.
Apply hot with brush. Used for muslin.

PAINTING

Probably few other structures require as
careful or as frequent painting as do green-
houses. This is due: First, to the moist con-
dition of the air in the house, which favors
the decay of the wood ; and second, to the dif-
ference in temperature between the outside
and inside of the house, which often causes
excessive contraction and expansion of the
structural material. It is especially important
that all joints in the framework be thorough-
ly coated when they are put together, and
that they be well painted in order to prevent

GLAZING AND PAINTING 115

moisture from entering. As a rule, green-
houses should be painted one coat both inside
and outside every second year, and inside
portions which are especially exposed to
damxpness and shade should be painted every
year, care being taken to see that they are
perfectly dry when painted. Nothing has
yet been found which will excel pure white
lead and oil with a turpentine dryer for this
purpose.*

For the outside the mtense white may be
softened by the addition of a little lampblack
or other coloring material, but for the inside,
colors are avoided, as they have a ten-
dency to absorb light. Pure white is un-
doubtedly best for interior painting.

Greenhouse woodwork when received from
the factory has usually been given a priming
coat. By special arrangement it is often pos-
sible to have it treated in a bath of hot lin-
seed oil or creosote. The latter will make it

*On this point commercial greenhouse builders do not
agree. One of the largest firms in the country uses
a paint containing 10 per cent, of French zinc and
finds it the most satisfactory paint they have ever
used. Another well-known firm after experimenting
with lead and zinc in varying proportions has gone
back to pure lead. The tendency of zinc paints is
to crack and peel, and of pure lead paints to become
chalky.

116 GREENHOUSES

almost proof against decay, but since the
joints must be coated with a thick paint
when the house is erected, and as the wood-
work is preferably white in order to make the
house as hght as possible, the extra expense
involved is hardly warranted. Creosote also
has a somewhat poisonous effect on some
greenhouse plants.

If the woodwork has not been primed
when received, it is preferably so treated be-
fore it is erected. Either pure, thin linseed
oil, or a mixture of oil and yellow ochre is
used for this purpose. As soon as erected,
the whole framework is painted inside and
out before glazing. After glazing another
coat is applied. Because of the frequent
painting necessary, it is seldom advisable at
the time of erection, to apply more than two
coats in addition to the priming coat.

Paints for Iron Work. — Ordinary paints
which are used for wood may also be used on
most unpolished metals. The oxidization of
iron and steel, however, is likely to stain
white paint, unless these metals are first
given a coating to prevent it. A good paint
for this purpose may be made by melting to-
gether three parts of lard and one part of
powdered resin. This is brushed on in a thin

GLAZING AND PAINTING 117

layer while hot. As soon as it is dry, ordin-
ary white lead paint may be applied with
little danger of its becoming discolored.
Shellac may also be used for the same pur-
pose.

Hot water and steam pipes cannot well be
painted with lead and oil paints on account
of the action of the heat. One of the most
satisfactory treatments for heating pipes is
to paint them with the so-called "aluminum"
radiator paint. This is light in color but
rather expensive. Paints which dry with a
glazed surface are said to interfere with the
radiating properties of heating pipes. A
dull drying black paint sometimes recom-
mended for this purpose is a mixture of lamp-
black and turpentine, to which linseed oil is
added not to exceed a fourth of the bulk of
the mixture.

Amount of Paint Required. — This varies
according to the kind and condition of the
surface to be painted, and to some extent
with the kind of paint used. Painters usually
figure that a gallon of mixed paint will cover
250 to 300 square feet of white pine or cy-
press the first coat, and 350 to 400 square
feet the second coat.

118 GREENHOUSES

A general rule for determining the amount
required is as follows: Divide the number
of square feet of surface to be painted by 200,
the result will be the number of gallons of
liquid paint required to give two coats.

Another is: Divide the number of square
feet by 18. The result is the number of
pounds of pure, ground, white lead necessary
for three coats.

Shading. — During the summer the heat
becomes so intense in a greenhouse that some
shade must be given if plants are to be grown
satisfactorily. This may be accomplished by
the use of muslin curtains in the inside of
the house or by lath screens laid upon the
roof. The most common method in com-
mercial houses is to apply some kind of a
coating to the outside of the glass which will
be washed off by the late fall rains. Some
form of whitewash is most satisfactory.

The author prefers a wash made of fresh-
ly-slaked stone lime and water, to which is
added one part of common salt to four parts
of lime. The salt is added after the lime is
slaked. This is then strained and applied
with a spray pump. It is usually necessary
to apply this two and often three times dur-

GLAZING AND PAINTING 119

ing the summer, but it comes off readily
through the action of the fall rains and frosts
and seldom requires the use of the scrub
brush.

Another paint sometimes used is com-
posed of white lead and gasoline, just enough
lead being used to make a milk-colored
liquid. This may be applied with a brush or
with a spray pump. It adheres much better
than the wash mentioned above, but is open
to the objection that it is sometimes neces-
sary to do considerable hand work to remove
it in the fall.

A third wash sometimes recommended is
made as follows : Slake a half bushel of
stone lime. Strain and add a brine made of
one peck of salt in enough warm water to
fully dissolve it. Then add three pounds of
rice flour, and boil to a paste. Then add a
half pound of whiting and one pound of glue
dissolved in warm water. Mix thorougfhlv
and let stand for a few days, thin with water,
and apply. This is the whitewash com-
monly used for painting fences and build-
ings and is very adhesive. For greenhouses
it is applied in a very thin coat.

Brackets. — In glazing and painting the

120

GREENHOUSES

outside of a roof, a common means of sup-
port for the workman is a plank supported
by brackets resting on the sash bars or on
every other sash bar.

Glazing Ladder. — Another device used
more in painting than in glazing is a ladder

Fig. 65. — Glazing ladder used in glazing and painting

made b}^ nailing cleats on one side of a plank
for foot holds, and on the other side longer
cleats so that they will rest across at least
two sash bars and thus distribute the weight.
The ladder is held in place by hooks which
reach over the ridge.

CHAPTER VIII

VENTILATION AND VENTILATING
MACHINERY

Greenhouse ventilation has not yet been
worked out with the same care and precision
as has the ventilation of dwellings, public
buildings, or even barns for the use of live
stock. On the other hand, greenhouses are
seldom or never built without some special
attention being given to the question of
ventilation, whereas, dwellings and even
public buildings are often erected without
any reference whatever to this important
subject.

This anomaly may be partly explained by
the following facts: (i) The transpiration of
l^lants is not so well understood nor is it so
easily measured as is the transpiration of ani-
mals. (2) Windows are necessary in dwell-
ings and public buildings to admit light and
they may be utilized, when necessary, to pro-
vide ventilation. (3) In greenhouses, ventila-
tion is not only provided for the purpose of

121

122 GREENHOUSES

maintaining a supply of fresh air, but is
utilized as a method of controlling tempera-
ture and humidity. (4) Greenhouses, be-
cause of their transparent roofs, are much
more liable to sudden or violent changes in
temperature (especially in days of alternate
clouds and sunshine) than are dwellings, and
the necessity for ventilation in order to
equalize the temperature is evident. (5)
Greenhouse plants are, as a rule, particular-
ly sensitive to cold drafts, and ventilation
cannot be left to the indiscriminate opening
of doors.

Systems of Greenhouse Ventilation. —

There can hardly be said to be any well de-
fined systems of greenhouse ventilation, as
compared with the so-called systems of
ventilation for public buildings. Greenhouse
ventilation rests on the principle that warm
air has a tendency to rise, and since the air
within the greenhouse is considerably warm-
er than that outside, during both summer
and winter, the question of changing the air
presents no serious problem. It is only
necessary to provide a means for the warm
air to escape. The cooler air from the out-
side easily finds its way into the house

VENTILATING

123

through the numerous small openings be-
tween the panes of glass.

Side Ventilation. — Side ventilation is of
little service, except during the summer
months, as the opening of these ventilators
in winter would expose the plants to a direct

Fig. 66. — Greenhouse showing A, side ventilators;
B, overhead or roof ventilators

current of cold air which would prove fatal.
Side ventilating sash are usually hinged at
the top and open outward and upward.
Probably less than 50 per cent, of the com-
mercial houses in the country are equipped
with side ventilation, though it is often con-

124 GREENHOUSES

venient in spring and summer. An in-
genious method is sometimes employed in
conservatories whereby the air is taken in
from below the benches and is warmed by
passing over the heating pipes. Thus the
danger of injury to the plants is greatly less-
ened. There is no evidence to show that
there is any special benefit to be derived from
these ventilators (Fig. 67).

Overhead Ventilation. — During the winter
practically all the ventilation of greenhouses
is accomplished by means of overhead
ventilators set in the roof at or near the
ridge. These ventilators are in the form of
sash hinged on the outside, and may be
closed down tightly over the sash bars or
opened to any degree desired. As the warm
air naturally rises, the opening of these
ventilators allows the warmest air of the
house to escape, and fresh cool air to filter
in through the crevices between panes of
glass without causing excessive drafts.

Experience shows that these ventilators
need, to be relatively narrow and practically
continuous along the whole length of the
house, rather than intermittent, as the pres-
ence of occasional large openings is more

VENTILATING

125

126 GREENHOUSES

likely to cause drafts of cold air. They are
preferably glazed with glass of the same
width as used for the roof and they should
be placed so that the bars of the sash will
be directly over the sash bars.

Size of Ventilators. — No definite rule can
be given as to the size of ventilators, as so
much depends on the location and arrange-
ment of the house, the kind of plants to be
grown, etc. Experience has shown that
where the ventilators are continuous along
the entire length on both sides of the roof,
the following sizes are sufficient.

Size of house Width of ventilating- sash

Up to 40 feet wide 24 inches

Above 40 feet wide 30 inches

This is the rule followed by most green-
house builders.

Methods of Hanging Sash. — Ventilating
sash may be hung so as to open either at the
top or bottom; that is, they may be hinged
at the lower side so as to open out and away
from the ridge, or they may be hinged at the
ridge so as to open upward from the lower
side. Both methods have their advantages
and disadvantages. Sash opening at the
ridge have the advantage that the air will

VENTILATING

127

escape more rapidly when the ventilators
are opened, as there is but little obstruc-
tion and the opening is at the highest part
of the house. There is also less tendency,
when ventilators are used on one side of

Fig. 68. — Two methods of hanging ventilator sash

the roof only, for unfavorable winds to
blow directly into the house.

The practical disadvantages of this meth-
od of hanging is that the ventilator sash
are more likelv to be torn off bv severe storms
than when hinged at the top, and also that
it is more difficult to prevent leakage at
the ridge. The prevailing tendency is to

128 GREENHOUSES

hinge the sash at the ridge and in houses 30
feet wide or more to provide ventilators on
both sides of the roof.

Operating Machinery. — Since the ven-
tilating sash are placed at the highest part
of the house, and as it is necessary to change
the size of the opening several times a day,
it is obvious that it is highly desirable that
some method be provided by which they may
all be opened and closed from some point
convenient for the operator. This is accom-
plished by means of various types of sash-
operating machiney.

The essential features on which most
types of ventilating machinery depend are
as follows: (i) A horizontal shaft firmly
fastened near the line of ventilating sash;

(2) a system of gearing, by which power ap-
plied at a point convenient to the operator
may be transmitted to and rotate this shaft;

(3) arms or levers attached to the shaft and
also to the sash, and so arranged that the
sash are raised or lowered when the shaft
is rotated.

Shafting. — The shafting generally used is
one inch or one and a fourth inch gaspipe.
The lengths are either riveted or clamped

VENTILATING

129

together by special couplings so that the
shaft will be perfectly rigid. A method
sometimes used is to screw the lengths of
pipe into an ordinary sleeve coupling as
far as they will go; drill a hole through each
end of the coupling and pipe, and rivet all
together with tight-fitting rivets. This
method is less satisfactory, however, than

Fig. 69. — Malleable iron shaft couplings

the use of split malleable iron castings sev-
eral forms of which are to be had. These
castings are longer and stronger than the
usual sleeve coupling and they thus have a
firmer grasp on the pipe.

They usually have pins or lugs cast in
the inside which fit into holes drilled in the
pipe at the proper positions, and the two
parts are clamped tightly in place by means
of bolts. A special advantage of this meth-

130

GREENHOUSES

od of coupling is that the shafting may be
put up in sections and clamped together after
being put in place. Square or round, solid
shafting is sometimes used, but it has less
torsional or twisting strength, weight for
weight, than does good wrought-iron or
steel pipe. Wrought pipe comes in two
weights, standard and extra heavy. It is
safe to use the different sizes and strengths
as follows: Shafts up to 50 feet in length,
I inch standard strength; shafts up to 75
feet in length, 40 feet of i inch extra heavy,
and 35 feet standard strength; shafts up to
125 feet in length, i/4 inch all extra heavy.

Shaft Hangers. — The shafting is held in
place by means of hangers. These hangers

Fig. 70. — Shaft hangers

may be fastened to the rafters, to the sash
bars or to the supporting posts. In iron frame
houses it is customary to hang overhead
shafting from the rafters and the shafting
for the side ventilators from the side posts,
using a hanger for each rafter or post.

VENTILATING

131

When the shafting is hung from the sash
bars a hanger is attached to every second
or third bar, usually to every second.

Fig. 71.-
Open col-
umn ventil-
ator gearing

i)«=5>

...fx.

Fig. 12.-
Open col-
umn chain
operated
ventilator
gearing

Gearing. — Generally speaking, there are
three types of gearing utilized for operating
overhead ventilator shafting. These are:
(i) The column gear, of which there are
many different forms; (2) the chain-oper-

132

GREENHOUSES

ated gear; and (3) the rack and pinion gear.
In the column gear a post or column sup-
ports the gearing and the wheel to which
the power is applied. One form of column
gear is known as an open column
gear, because the drive rod is not
inclosed in the column and there
is no housing about the gearing.
In another open column gear
type a chain is used to transmit
the power. In the closed col-
umn types all gearing is inclosed
and runs in oil, much the same as
in the transmission case of an
automobile. This insures free-
dom from noise and ease of
operation.

In the chain type no columns
are required, a feature much
prized by growers. By this sys-
tem practically all the ventilators
in a house may be operated from
one point, as the chains may be
run almost anywhere in the house
by the use of pulleys. The ab-
sence of columns means less shade.

The rack and pinion type differs from
the two general types mentioned above, not
so much in the method of applying the power

Fig. 73.—
Closed col-
umn ventil-
ator gearing

VENTILATING

133

Fig. 74. — Chain system of operating ventilators. No

columns used

Fig. 75. — Rack-and-pinion system of operating
ventilators

13i GREENHOUSES

to the shaft as in the method of actually
opening the ventilators. The chief advan-
tage of this system lies in the fact that there
is less torsional or twisting strain on the
shafting than when the usual method is em-
ployed, and they are more powerful. The
chief disadvantage is that provision must be
made for giving the shaft several revolutions,
while a half or two-thirds revolution is usual-
ly sufficient with the more common forms.

Some practical growers claim that the rack
and pinion device is very subject to wear and
is a frequent cause of trouble. This is more
especially true of the older forms of this type.
The fact that they are not generally used
would seem to indicate that practical growers
as a rule are not yet convinced of their super-
iority, though they are now being installed in
some large houses where it is necessary to
operate long runs.

Quite frequently the hand wheel and gear-
ing are fastened to the rafters or purlin posts
and no extra columns are required.

Side Ventilating Machinery. — The essen-
tial features of side operating machinery
are the same as for overhead ventilators.
When there are side benches a shaft is

VENTILATING

135

Fig. 76. — Ventilators (a and b) operated by means of
rods twilh universal joints attached to posts and
rafters. No extra columns are necessary.

usually used and the hand wheel placed at a
convenient position for the operator. When
there are no benches along the sides a com-
pact device is advisable in order to take up as
little room as possible (Fig. 78).

136

GREENHOUSES

Fig. n. — Device for
operating side Ventilators

Ventilator Arms. —

Ventilator sash are
most commonly raised
and lowered by means
of hinged braces or
arms operated from
the shafting. There
are three general
types.

The elbow arm is
most commonly used
but has the disadvan-
tage that a long lever-
age is required, in order to open the venti-
lators to the full width, which puts a consid-
erable strain on the shaft.

The double acting arm overcomes this dif-
ficulty to some extent as it is possible to se-
cure a wider opening with a shorter leverage,
but it is necessary to rotate the shaft
through an extra half turn. On long runs
these arms are now being extensively used in
place of the common elbow arm.

The extending arm is used in low houses,
or for side ventilators, or in other places
where an elbow or double acting arm would
extend into the house so far as to be in the

VENTILATING

13T

way. It folds together when the sash is
closed and occupies little space, but it ex-
tends automatically when the shaft is turned.
It is especially convenient under certain con-
ditions, but it lacks the strength necessary
for long runs.

Fig. 78. — Compact machine for operating side ventilators

In all systems the arms are clamped se-
curely and rigidly to the shafting, and as
near as possible to the hangers so as not to
spring the shafting when heavily loaded.
They are spaced about 3 feet apart along the
sash. If continuous sash are not used the
arms should be distributed as follows: For
sash up to 4 feet long, one arm ; from 4 to 7

138

GREENHOUSES

Fig. 79. — Types of ventilator arms, A. double acting-
arm; B, elbotw arm; C, extending arm closed; D, extend-
ing arm open

VENTILATING 139

feet long, two arms; and from 8 to ii feet
long, three arms, etc.

Capacity of Ventilating Apparatus. — The

capacity of ventilating apparatus depends
largely upon the size and method of manu-
facture, but the length of run is limited to
the torsional strength of the shafting. In
long lengths there is always more or less tor-
sion, so that the ventilators at the extreme
end do not open as wide as those close to
where the power is applied. This is of little
consequence in summer when the ventilators
are wide open, but in winter, when only
slight ventilation is required, it may result in
the sash at the end of the shaft not open-
ing at all and the ventilation will thus be un-
even and unsatisfactory. Moreover, the sash
are likely to be frozen down in winter and
the tendency for the shafting to twist is thus
increased. It is wise to have a wide margin
for safety.

An indication of the length of shafting
that may be used with safety is given on
page 130. Tests show that one and a
fourth-inch standard pipe has a torsional
strength 42 per cent, greater than i-inch

140 GREENHOUSES

double-strength pipe and that the weights
are practically the same. The price of i-
inch double-strength pipe averages about 25
per cent more than standard one and a fourth
inch pipe. It is evident, therefore, that for
long runs it is not only safer but more
economical to use one and a fourth-inch
standard pipe than i-inch double-strength.

Generally speaking, a 150-foot run is about
the limit when elbow arms are used. This
may be slightly increased by using the
double acting arms, and still further by us-
ing the rack and pinion system. This is
equivalent to saying that the ventilators in a
house 300 or 350 feet long may be operated
from one station by having machines located
in the center of the house and operating each
way. It is economy to have all ventilator
sash for one house operated from the same
station if possible.

Sliding Shaft System. — In order to enable
the operator to care for an extremely long
line of sash from one station a sliding shaft
system has been devised. In this case the
shafting is solid and square, and instead of
rotating it slides backward and forward, the
motion being given by a pinion working on
a screw or worm gear at one end of the shaft.

VENTILATING

141

Fig. 80. — Sliding- shaft system for operating ventilators

This sliding movement is utilized to
operate the sash by means of a right angle
lever, pivoted at the angle with the short arm
attached to the shaft and the long arm to the
sash. It is claimed for this system that it
will operate a line of sash 500 feet long.

CHAPTER IX
BEDS, BENCHES AND WALKS

In the earlier greenhouses, plants were al-
most always grown on raised benches. This
was partly for the convenience of the grow-
er and partly because the houses were almost
always erected with high, solid, side walls
and it was necessary, in order to secure satis-
factory growth, to bring the plants close to
the glass roof. In modern houses, when all
or part of the side walls are of glass, raised
benches are not so necessary, and are very
commonly dispensed with and the plants
grown directly in the soil which forms the
floor. This is particularly true when vege-
tables such as lettuce, tomatoes or cucum-
bers are grown.

Florists, as a rule, have been loth to give
up the use of benches and present the follow-
ing arguments in their favor, (i) It is
more convenient to care for plants when
grown on raised benches than when grown
on the ground. (2) Benches make possible

142

BEDS, BENCHES AND WALKS

143

O
2;

bib

144 GREENHOUSES

the placing of the heating pipes underneath,
which makes them less conspicious and at
the same time affords a method of giving
''bottom heat/' which is considered advant-
ageous with many plants. (3) It is main-
tained that there is a better circulation of
air about plants grown on benches and that
the plants are less subject to disease. (4)
The temperature and moisture of the .icil
can be more easily regulated in benches.
(5) Low-growing plants make a better dis-
play when grown on benches.

The following are the most common dis-
advantages claimed by those who urge
against the use of benches, (i) They are
expensive to build and maintain. (2) They
do not admit of an economical use of space.
(3) The soil dries out rapidly. (4) The soil
has to be changed more often. (5) It is
more difficult to use labor-saving tools such
as wheel-barrows. (6) All work must be
done by hand. In large houses it is possible,
when plants are grown on the ground, to pre-
pare the soil with a horse or with wheel hoes.
(7) With high-growing plants such as to-
matoes and cucumbers, it is difficult to har-
vest the crop when they are grown on high
benches.

BEDS, BENCHES AND WALKS 145

Fig. 82. — Tomatoes growing in solid raised beds

Fig. 83. — Solid raised hods of hollow building tile in use
at the Michigan Agricultural College

146 GREENHOUSES

Raised Beds. — To overcome some of the
objections to raised benches, many growers
use soHd raised beds, the height varying from
a few inches to that common for benches.
Such beds dry out less cjuickly than do
benches, the soil does not have to be removed
as frequently, and they are less expensive to
maintain. They are open to some of the ob-
jections urged against benches and do not
possess many of the advantages afforded by
culture in the open soil. The width and ar-
rangement follows closely that of benches.

Raised Benches. — Benches are exposed
continuously to conditions which favor their
rapid deterioration. Unless well constructed
of good material, they are a source of con-
stant annoyance. Many growers use wooden
benches. Others use benches having iron
frames, and sides and bottoms of wood, tile,
slate or cement slabs. Still others use solid
concrete benches. All forms have their ad-
vantages and their advocates.

Wood Benches. — Wood benches have the
advantage of slightly less first cost, though
if good material is used, the cost will be near-
ly as great as for iron frame benches. In
permanent houses nothing but cypress or

BEDS, BENCHES AND WALKS

147

cedar should be used, genuine pecky cypress
being undoubtedly the best. The sides
and bottom boards are not less than i inch
thick. The side boards are 8 inches wide.

11MI/H

Fig. 84. — Two types of wood benches. A, bottom boards
running lengthwise; B, bottom boards running crosswise

The width of the bottom boards is imma-
terial, except that when in place they have a
space of a fourth-inch between them for
drainage. They are usually run length-
wise of the bed and are supported by cross-
beams, spaced not more than 4 feet apart.

The size of the cross beams will depend
somewhat on the width of the bench, as
follows:

For benches up to 4 feet wide 2x4 inches

For benches from 4 to 6 feet wide.... 2x6 inches
For benches over 6 feet wide 2x8 inches

The legs or posts are at least 4x4 inches
in size, and rest on concrete or brick piers.
Sometimes, when cement walks are used,
they are made to extend under the benches
far enough to act as a foundation for the
posts.

GREENHOUSES

To guard against warping of the side and
end boards of wood benches, angle irons
may be used in the corners and along the
sides, and fastened by screws or small bolts.
Brick piers may be used in place of the
wooden legs. The wooden legs, however,
will usually outlast the bottom boards and
cross-beams.

Fig, 85. — A type of iron frame bench

Iron Frame Benches. — In the majority of
iron frame benches, i-inch wrought-iron
pipe is used. It is rarely threaded but is tied
together with split malleable iron castings
by the use of bolts and set screws. The
sides and bottom may be made of wood, iron,
slate, tile or even of cement slabs. All are

BEDS, BENCHES AND WALKS 149

removable and may be replaced without tak-
ing down the frame.

Iron frame benches with cypress sides and
bottoms are now much in favor. They are
but little more expensive than the all-wood
benches and are in most cases more satis-
factory, as the frames are nearly indestruct-
ible. They should, however, be made of
wrought-iron pipe rather than of steel.
They may be had in two forms, one in which
the bottom boards run lengthwise of the
bench and another in which they run cross-
wise. The advantage of the latter is that
short lengths may be used. These benches
may be purchased with all parts cut to order,
or they may be easily cut by anyone familiar
with pipe cutting.

Iron frame benches are also made of angle
iron or structural iron of different forms.
The chief disadvantage of these is that the
iron cannot l)e worked readilv bv the ordin-
ary workman and must be cut and fitted at
the factory.

Concrete Benches. — Concrete, because of
its permanency, is often recommended for
greenhouse benches, and its use is increas-
ing. In general, there are two separate

150

GREENHOUSES

BEDS, BENCHES AND WALKS 151

types. In one type the legs, bottom and
sides are cast separately in molds and then
put together in the greenhouse. In the other
type the whole bench is cast in a form built
in the house where it is to stand. There
are at least two firms having patents on
cement greenhouse benches and who are pre-
pared to sell or rent molds or forms for mak-
ing them. It is also possible for a skilled
mechanic to make forms to suit any special
location or for any form of bench. In mak-
ing concrete benches, care should be taken
to provide for adequate drainage through the
bottom and to see that they are thoroughly
reinforced.

There has been some discussion as to the
effect of concrete benches on the growth of
plants. The author has had but little prac-
tical experience with them but quotes from
one of the largest users of concrete benches
in the country, as follows:

"At my place I use only concrete benches
and the results and advantages .have been
very satisfactory, but I want to be open and
frank concerning the disadvantage, which is
only for the first year. Something in the
line of a chemical of a whitish nature ap-
pears on fresh new cement, and that seems

152 GREENHOUSES

to be injurious to plants; but after you have
filled the benches with soil and used them
the first year, the soil generally eats or ab-
sorbs this chemical, and the roots of carna-
tion plants or anythmg else cling to the ce-
ment slabs the same as they do to slate. A
good remedy to get rid of this so that it will
not injure the plants is simply to put air-
slaked lime or rather heavy whitewash on
the inside of the bench, and that seems to
protect the plants from coming in contact
with the chemical mentioned/'

Height and Width of Benches. — The

height of greenhouse benches is largely de-
termined by that most convenient for
the operator to work. This in turn depends
upon the nature of the plants to be grown.
For example, when low-growing plants like
lettuce are grown, a bench 32 inches high is
about right ; but when carnations are grown
this may be so high as to make disbudding
difficult. This refers to the distance from
the top of the walk to the top of the sides
of the bench.

The width of the" bench depends on the
width of the house, on the arrangement of
the benches, and to some extent on the kind

BEDS, BENCHES AND WALKS 153

of plants to be grown. It is limited to the
distance a man can conveniently reach in
caring for the plants. This distance is
about 2>^ feet or rarely 3 feet. In other
words, benches that can be worked from
one side onlv should be no more than 2>^ or
3 feet wide, and benches which may be
worked from both sides should be no more

Fig. 87. — Method of arranging benches in an uneven-
span house to secure best advantage of the sunlight

than 5>^ or rarely 6 feet wide. In uneven
span houses it is sometimes advisable to ele-
vate the walks and benches.

Arrangement of Benches. — This is gov-
erned by the width of the house, the use for
which the house is designed, the height of
the beds or benches and by the individual
preference of the owner. Commercial grow-

154

GREENHOUSES

ers look upon walks as waste space and en-
deavor to keep them as narrow as is con-
sistent with ease and economy in getting
about the houses. In private houses, con-
servatories and show houses, the walks are
sufficiently wide to allow two persons to pass
easily.

30-

—

-5.-

-5-

Fig. 88. — An arrangement of benches in a 30-foot house.
Only 66 2-3 per cent of the floor space
available for crops

In figures 88 and 89 are illustrated two
methods of arranging benches in a 30-foot
house. By the first method four benches,
each five feet wide, are provided and 661 per
cent of the floor space is available. By the
second method three wide and two narrow
benches are provided and 733 per cent of the
floor space is available. In the latter method

BEDS, BENCHES AND WALKS

155

the side benches extend the entire length of
the house and one walk is eliminated.

It is worth while to exercise considerable

care in determining the arrangement of
the benches, especially in commercial houses.
As a rule a walk along the side of a house
is an extravagance. When the width of the

—Z>0'

-^±-

-;t

--/-S"-

Fig. 89. — Another arrangement of benches in a 30-foot
house. By this arrangement 7Z 1-3 per cent of the floor
space is available for growing crops

house admits, it is usually more economical
to have narrow benches along each side.

When low beds are used, the walks may
be narrower than with high benches as peo-
ple can pass more readily. Tn conserva-
tories and show houses 3 feet is none too

156 GREENHOUSES

wide. In commercial houses with high
benches, from 20 to 24 inches is a common
width. When low beds are used, the walks
are sometimes as narrow as 14 or 16 inches.
It is often advisable to arrange the
benches so as to have the center walk of ex-
tra width, which will allow of the use of
a wheel barrow or cart in removing and re-
plenishing the soil and for other purposes.

Material for Walks. — Concrete is unques-
tionably the best material for walks. Water
has no effect on it; it is substantial; it may
be used as a foundation on which bench legs
and ventilator columns may stand; and it
may be quickly and easily laid. In conserv-
atories and private houses nothing can take
its place. For data on concrete construction
see Chapter XIV.

In commercial houses coal ashes are often
used. Ashes must be kept away from the
pipes as the sulphur they contain will cause
the pipes to corrode very rapidly.

Curbs. — For convenience and cleanliness,
many growers who plant directly on the
ground prefer to have their houses marked
oft' into regular beds, divided by narrow
walks and surrounded by a curb to keep the

BEDS, BENCHES AND WALKS 157

soil in place. In time, the constant addition
of manure raises the soil in these beds so
that they become in reality raised beds.
Board or plank curbs are rarely satisfactory,
as the moisture of the soil on one side causes
them to warp. The most satisfactory and
economical curbs are made of concrete,
which is heavily reinforced with iron rods
when it is poured.

CHAPTER X
GREENI-IOUSE HEATING

Generally speaking, there are only two
satisfactory methods of greenhouse heating:
Steam and hot water. Direct heating by
stoves is not satisfactory even in small
houses, and no satisfactory system has yet
been devised for the use of hot-air furnaces.
The only method aside from steam or hot
water which deserves mention is heating by
flues. They are wasteful of fuel, and their
use is not justified, except in cheaply con-
structed houses which are used only for a
few months in the spring or fall.

The principles pertaining to greenhouse
heating are much the same as those involved
in heating other buildings, except that the
loss of heat is greater from glass than from
wood or brick walls, and a higher and more
constant night temperature is required than
is necessary in dwellings. For this reason,
relatively more radiating surface is required
and boilers of larger capacity are needed.

158

GREENHOUSE HEATING 159

Heating with Flues. — In heating with
fines the equipment consists simply of a
furnace at one end of the house and a chim-
ney at the other, the two being connected by
a flue, carried underneath the bench or
buried just underneath the soil, through
which the heat and smoke are carried. This
may be made of brick, but large-size drain
or sewer tile are more commonly used. These
withstand the heat and are easily and cheap-
ly put in place. It is best to have the flue
slope upward slightly toward the chimney.
As has already been stated, this method is
wasteful of fuel. It is also difficult to regu-
late. It is still employed to some extent
by vegetable gardeners in cheap houses,
used only in late winter or early spring for
the starting of early vegetable plants, sweet
potatoes, etc.

Hot Water vs. Steam. — There has been
much discussion as to the relative virtues of
hot water and steam for use in greenhouse
heating. It may be well to consider here
some of the advantages claimed for each.
For hot water the followinof are claimed:
(i) It provides a more even heat than steam.
(2) The radiating pipes are not so hot, and

160 GREENHOUSES

plants near them are less likely to be injured
than when steam is used. (3) It requires
less frequent firing, since warm water is al-
ways circulating in the pipes as long as there
is any fire in the furnace, whereas, with
steam it is necessary to keep the water boil-
ing to keep steam in the pipes. (4) For the
above reason a night fireman is not required
in small houses equipped with hot water. (5)
It is less dangerous. This is more apparent
than real, for steam is usually carried at low
pressure. (6) It is claimed that hot water
requires less fuel. Theoretically this should
be true, but in practice it has not been very
definitely proven. (7) Water will hold heat
for some time if the fire should accidentally
go out.

The following advantages are claimed for
steam: (i) Less cost of installation. (2)
Steam requires fewer radiating pipes hence
less shade is cast when the pipes are placed
overhead than when hot water is used. (3)
Less time is required to get up heat, as there
is a relatively small body of water. (4) A
greater area may be warmed from a given
heating plant than with hot water, for the
steam may be forced farther, (s) A steam

GREENHOUSE HEATING IGl

plant may be used to furnish steam for soil
sterilization.

All the above apply more especially to
small ranges than to large ranges. As a
rule, hot water is more generally used in
ranges covering up to 20,000 square feet and
steam in larger ranges, although there are
many exceptions. At present the tend-
ency seems to be toward the use of hot water
rather than steam.

In an investigation recently made by the
author among a large number of greenhouse
owners, 86 per cent, of those having 20,000
square feet or more under glass preferred
steam heat. The chief reasons stated were,
"better control," "cheaper maintenance," and
"less shade from pipes." Six per cent, pre-
ferred a combination of hot water and steam.
The remaining 8 per cent, preferred hot
water, stating as their reasons, "steadier
heat," "plants grow better," "pipes do not
rust out during the summer as with steam,"
and "cheaper to operate in spring and fall
when little heat is required."

Of those having less than 20,000 square
feet under glass, 74 per cent, preferred hot
water, giving in addition to the reasons

162

GREENHOUSES

o .- 5 c

0\ u. l^ cS

GREENHOUSE HEATING 163

named above, ''less labor to fire, especially at
night" and "needs no night fireman/'

Combination Systems. — A combination of
hot water and steam may often be used to
advantage. By this means steam may be
had for power and at the same time be util-
ized for heating. In cold weather both boil-
ers may be used for heating, while in mild
weather the steam boiler alone may be used,
thus furnishing the necessary heat and
power.

Another and more simple combination of
hot water and steam heating which, how-
ever, is more expensive in installation, con-
sists of two separate sets of heating coils,
one of which is connected with a steam boil-
er and the other with a hot water boiler. The
steam is used when a small amount of heat
is needed quickly on cold nights in early fall
or late spring, and to supplement the hot
water in severe winter weather.

In any system of heating it is much safer,
as well as more economical in operation, to
install two or more boilers rather than to
depend on one large one. Both may be
used in severe weather and in case of acci-
dent to one, the other may be forced for a

164 GREENHOUSES

few days and thus protect the plants from
injury by freezing, which would inevitably
result if only one boiler was in use.

Heating Coils. — Because of the large
amount of heating surface required, and be-
cause all parts of a greenhouse must be kept
at as nearly uniform temperature as possible,
radiators such as are used in private houses
have not been found practicable in green-
house heating. Instead, long coils of
wrought iron or steel pipe are used. For
steam heating these coils are commonly of
I or iM-inch pipe. In hot water heating they
are slightly larger, varying from i/4 to 2
inches. In the early days of hot water heat-
ing large cast-iron pipe, often as large as
four or five inches in diameter was used. It
is still used to some extent, but more often
in small private conservatories than in com-
mercial houses.

There is very little to be said in favor of
using cast-iron pipes. The fact that they are
now so little used shows that they have no
special merit. The smaller, wrought pipe is
lighter and much more easily handled; is
screwed together instead of caulked "with
lead and oakum; has much more radiating

GREENHOUSE HEATING

165

surface in proportion to the volume of water
contained; can be placed along the side
walls or hung on the supporting posts in-

Fig. 91. — Under-bench heating with large cast-iron

pipes

stead of having to be supported on mason-
ry piers ; and permits of a more perfect con-
trol of the heat.

166 GREENHOUSES

Heating coils are made by joining several
pipes together by means of headers. The
hot water is conducted to the coils from the
boiler by means of a larger pipe known as
a flow pipe or feed pipe. It is returned to
the boiler by means of a return pipe. In
steam heating the coils are often so arranged
that the water formed from the condensed
steam returns to the boiler through the flow
or feed pipe, instead of through a separate
return pipe.

,. j.'"

CHAPTER XI
HOT WATER INSTALLATION

General Principles. — Before discussing
the installation of a hot water heating sys-
tem it is necessary to have in mind the phy-
sical and mechanical principles involved.
Briefly they are these: Water increases in
volume as it is heated and it is consequently
Hghter in weight. When a fire is lighted un-
der a water boiler the water around the heat-
ing surface expands and, being lighter, is
forced upward by the heavier, colder water.
Popularly speaking, the hot water ''rises."

The practical problem is to conduct the
hot water from the boiler to the coils where
the large radiating surface permits the water
to give up its heat to the air in the house
and then, as it becomes colder and heavier,
to conduct it back to the boiler where it will
displace the warmer and lighter water there.
Gravity is the force utilized to produce cir-
culation. It acts with a force proportional
to the difference in weight between the col-
umn of warm water and the column of cool
water.

167

168 GREENHOUSES

The following table shows the weight of a
cubic foot of distilled water at different
temperatures.

32 degrees F.. 62.42 pounds 170 degrees F.. 60.77 pounds

100

....62.02 "

180

..60.55

110

....61.89

190

..60.32

120

....61.74

200

..60.07

130

....61.56 "

210

..59.82

140

....61.37 "

220

..59.76

150

....61.18 "

230

..59.37

160

....60.98 '•

From the above table it is apparent that a
cubic foot of water entering the boiler at 140
degrees is 0.82 pounds heavier than an equal
quantity leaving the boiler at 180 degrees.
It is evident that the higher the columns of
water the greater will be the difference in
weight, and consequently the more rapid will
be the flow.

The various factors influencing the veloc-
ity of water in a gravity hot water system
are embodied in the followingf formula.

'fe

Y^^ / 2gh (w— W)

V (w+W)

In this formula, V=the velocity in feet per
second, g=the force of gravity (32.16), h=
the total height of the system, W=the weight
of a cubic foot of water wdien it leaves the

HOT WATER INSTALLATION 169

boiler and w=the weight of a cubic foot of
water when it enters the boiler.

This, of course, disregards friction. The
practical application is that when it is de-
sired to increase the velocity of the water;
e.g. in long runs, it may be done by either
lowering the boiler or by raising the height
of the flow pipes.

The following table shows the velocity in
feet per second in a hot water system under
various conditions.

Height Difference in temperature on leaving and

of entering boiler

Column 5° . 10° 15° 20° 30° 40°

Feet Per second

5 ft. 0.541 0.750 0.922 1.09 1.33 l.Sl

10 " 0.765 1.06 1.32 1.55 1.88 2.04

20 " 1.085 1.50 1.85 2.19 2.66 3.01

30 " 1.35 1.83 2.26 2.68 3.26 3.71

Arrangement of Piping. — There are two
approved methods of arranging the piping
for hot-water heating. One is known as the
''down hill"; the other as the ''up hill.'' In the
former the highest point in the system is
directly above the boiler. In the latter the
highest point is at the end of the system
farthest from the boiler. Either is satisfac-
tory and is preferred to the "level" system
sometimes advocated. In either the "down

170

GREENHOUSES

hill" or the "up hill" system the air which
collects in the pipes will eventually reach the
highest point when it may be allowed to
escape through an automatic air valve. In
the "level" system slight sags and raises are
likely to occur and the air will collect in the
higher parts and cause trouble.

Fig. 92. — Diagram showing "down-hill" and "up-
hill" systems of piping. A, boiler; B, flow pipe;
C, C, headers; D, radiating pipes or coils; E, re-
turn pipe; F, automatic air valve; x indicates
height of water column

The author prefers the "down hill" system
when the flow pipes are carried in the upper
part of the house and the coils are consider-
ably lower. When all the pipes must be in
the lower part of the house, or under the
benches, he prefers the "up hill" system. The

HOT WATER INSTALLATION

171

Fig. 93. — A type

of automatic air

valve

majority of greenhouse oper-
ators seem to be in accord
with this view. Practically
speaking there appears to be
but little difference in the
efficiency of the two systems
and the convenience and the
arrangement of the house de-
termines the choice to a con-
siderable extent.

Estimating Radiation. —

The calculations for green-
house heating are based on
certain fundamental facts which for hot
water may be stated briefly as follows: A
square foot of glass will give off, under or-
dinary greenhouse conditions in winter
weather, approximately i B. T. U-"^ of heat
per hour, for each degree difference in tem-
perature between the air inside the green-
house and that outside. A good wood, brick
or concrete wall will give off about a sixth
as much, or a sixth B. T. U. per square foot
per hour. It is customary to divide the total
wall surface by six and consider it as equiva-
lent to glass.

*British Thermal Unit; the amount of heat required to
raise one pound of distilled water from 62 to 63
degrees F.

172 GREENHOUSES

To arrive at an estimate of the possible
heat loss from a greenhouse add to the total
square feet of exposed glass surface a sixth
of the total square feet of exposed wall sur-
face, and multiply the sum by the difference
between the temperature at which the house
is to be kept and the lowest outside tem-
perature which will probably be experienced.
Suppose, for example, that a house has
10,000 square feet of glass and equivalent
glass, that it is desired to keep it at a night
temperature of 50 degrees, and that the low-
est outside night temperature to be expected
is — 10 degrees. The number of B. T. U.
given off by such a house under these con-
ditions would be [50° — ( — 10°)] x I X 10 x
10,000 or 600,000 B. T. U., and enough heat-
ing coils must be provided to supply this
amount.

In hot water heating the coils will give
off approximately two B. T. U. per square
foot of surface per hour for every degree
difference in temperature between that of
the coil and that of the surrounding air. The
average temperature of the coils may be
taken to be 160 degrees, and if the house is
to be maintained at 50 degrees the difference
will be no degrees. Multiplying no by 2

HOT WATER INSTALLATION 173

we have 220 or the number of B. T. U. given
off by each square foot of radiating surface
per hour. If, then, we divide 600,000 by
220 we have 2.,y2y which is the number of
square feet of radiating surface to be pro-
vided.

These principles may be embodied in the
following formula where R= the amount of
radiating surface required in square feet; T,
the temperature to be maintained inside the
house; t, the lowest outside temperature to
be expected; and G, the number of square
feet of glass and equivalent glass.

^^(T-t) X G
(160-T) 2

This formula gives a wide margin of safe-
ty. Most builders prefer to use consider-
ably less radiating surface and depend on
forcing the furnace in extremely cold
wxather. By so doing the temperature of
the coils may be kept at 180 degrees or even
considerably higher under favorable condi-
tions and the amount of radiation required
will be correspondingly less.

Amount of Pipe Required. — Having esti-
mated the amount of radiation required the
next problem is to find the quantity of pipe

174

GREENHOUSES

necessary to provide this amount. For ex-
ample, I linear foot of i>^-inch pipe furnishes
about half a square foot of radiating surface.
Divide the number of square feet of radia-
tion required by the outside area of a linear
foot of pipe of the desired size. The result
will be the number of linear feet of pipe re-
quired. From this is subtracted the
amount of radiation supplied by the flow or
feed pipe and other fittings.

The following table gives the radiating
area in square feet of a linear foot of pipe of
various sizes.

Size of pipe

Radiating surface of
1 linear foot

1/2

3/2
4

inch 0.27 square feet

0.35

0.43

0.49

0.62

0.75

0.91

1.05

1.18

For practical purposes the following gen-
eral rule will give approximately the
amount of radiating surface required. Divide
the number of square feet of glass and

HOT WATER INSTALLATION 175

equivalent glass:

By 6 to heat the house to 40 degrees
By 4 to heat the house to 50 degrees
By 3.5 to heat the house to 60 degrees
By 3 to heat the house to 70 degrees

The quotient will be the square feet of
radiating surface required.

Size of Flow Pipe. — Having determined
the amount of radiation necessary, the next
problem is to determine the size of the flow
or feed pipe required to supply the coils.
Experience has shown that it is not necessary
for the supply pipe to be equal in capacity
to the sum of the capacities of the coil pipes.
The correct size may be determined, theo-
retically, by the use of the following rather
tedious formula:

A=. ^^

25wvt

In this formula A=the cross section
area in square inches of the flow pipe;
H, the total radiation in B. T. U. per
hour given off by the coils; R, the radiating
surface in square feet; w, the weight of the
water per cubic foot; v, the velocity of feet
per second; t, the difference in temperature
between the water when it leaves the boiler
and when it returns.

This formula is seldom used but the fol-

176 GREENHOUSES

lowing table has been derived from it. To
use, measure the height of the water column
in feet, find from the table the factor for this
height, and multiply the square root of the
radiating surface in square feet by this fact-
or. The result will be the size of the flow
pipe, in inches (diameter) required. This
is based on the assumption that there is a
difference of lo degrees in temperature be-
tween the water when it leaves and when it
enters the boiler.

Height of
Column (ft.) Diameter Factor

5 0.133

10 0.113

15 0.104

20 0.095

25 0.091

30 0.187

For example, to supply a coil of ten ij^-
inch pipes lOO feet long (500 square feet)
15 feet above the bottom of the boiler, would
require a feed pipe the diameter of which

would be represented by V500 x 0.104 equals
22.4 X 0.104 equals 2.33 or a 2i/2-inch pipe.

Short Methods. — The above formula
takes into consideration the fact that the
greater the height of the column of water
the more rapid the flow and consequently

HOT WATER INSTALLATION 177

the smaller may be the supply pipe used. In
greenhouse heating, however, the height is
seldom very great, usually varying between
8 and 20 feet, so that the following rule of
thumb usually proves satisfactory. The flow^
pipe should be one pipe size greater in dia-
meter (inches) than the square root of the
radiating surface of the coil (in square feet),
divided by 10. Applying this rule to the

above problem we have V 500 -^10=^2.24
The next pipe size is 2/4 inches but this is
so close to the estimated size that a 2>^-inch
pipe should be used to insure efficiency.

The size of the main supply pipe from the
heater is determined in the same manner by
taking the sum of all the radiating surface
to be supplied. It is better to have one main
flow pipe leading from the boiler, from
which branches to the various coils may be
taken, than to have a flow pipe direct from
the boiler for each coil, though two or more
flow pipes may be taken ofif. The return 1
pipes should be of the same size as the flow
pipes. The flow pipe is taken from the top
of the boiler and the return pipe enters at
the bottom.

In Fig. 94 is shown a diagram of a method
for piping a medium-sized house. In the dia-

178

GREENHOUSES

Fig. 94. — ^A method of piping a medium size house

gram A is the flow pipe extending directly
up from the boiler; B, B, branch flow pipes;
C, C, branch flow pipes extending the length
of the house; D, D, distributing pipes at the
opposite end of the house; E, E, E, E, the re-
turn coils; F, F, F, F, return pipes; and G,
expansion tank.

Valves should be conveniently placed so
that any or all of the coils may be cut off in-
dividually. They may be placed either in the
flow or return pipe, or in both. If there is a
valve in both the supply and return from each
coil, any one may be repaired in case of an
accident without drawing the fire or inter-

HOT WATER INSTALLATION

179

?^ ^

Fig-. 95. — Diagram showing under-bench method of hot
water piping. A and B flow pipes; C and D heating coils

fering with the circulation in the other coils.
The valves should be of a type which, when
open, cause as little resistance to the flow of
water as possible.

Length of Coils. — The length of the coils
which may be used depends: (i) Upon the
height of the column of water; (2) upon the
size of the pipes which make up the coils;
and (3) the amount of friction in the coils
and fittings. The length of coils which may
be satisfactorily used with pipes of various
sizes are given in the following table.

180 . GREENHOUSES

Size of pipe Length of coil

1 inch Up to 50 feet

1^ inch 50 to 75 feet

V/2 inch 75 to 100 feet

2 inch 100 to 150 feet

This table is based on the supposition that
gravity, only, is to be depended upon for
circulation. When pumps are used to cir-

Fig. 96. — Gasoline engine arranged to circulate hot twater
in a greenhouse heating system

HOT WATER INSTALLATION 181

culate the water the length may be materially
increased.

The most commonly used size is i/^-inch,
and when the houses are much over lOO feet
in length two or more coils may be used,
each extending only a part of the length, and
having separate feed and return pipes.

Expansion Tank. — Water expands in
heating. It is necessary, therefore, to make

some provision to take care of the expan-
sion, in order that the pipes shall not burst
and to keep them full at all temperatures.
This is accomplished by connecting the sys-
tem with an expansion tank into which the
excess water will flow as it expands, and
from which it will flow back into the system
as it cools. It is placed at or above the high-
est point in the system, but it may be con-
nected with any part of the system or even
with the boiler.

The size of tank required is directly
proportional to the volume of water con-
tained in the system and is determined by
the amount of expansion resulting from
heating. The following table adapted from
Kent shows the relative amount of expansion.

182

GREENHOUSES

Temperature
Cent.

4°

10°

20°

30°

40°

50°

60°

70°

80°

90°

Temperature
Fahr.

Comparative
Volume

39.1° l.OOOOO

50. ° 1.00025

68. ° 1.00171

86. ° 1.00425

104. ° 1.00767

122. ° 1.01186

140. ° 1.01678

158. ° 1.02241

176. ° 1.02872

194. ° 1.03570

100'

.212.

1.04332

From the above table it will be seen that
the increase in volume from 50 to 212 de-

Fig. 97. — Automatic expansion tank. This is con-
nected with the city water system and will auto-
matically keep the heating system filled. See also

G, Fig. 94

HOT WATER INSTALLATION 183

grees is 1.04432 — 1.00025=0.04307, or a little
more than 4 per cent. It is customary to
make the expansion tank large enough to
hold 5 per cent, or a twentieth of the water
contained in the system, including the boil-
er. Thus, if the system contains 100 gal-
lons, the supply tank should be large enough
to hold a twentieth of that amount or 5
gallons.

The capacity in gallons of a linear foot of
standard wrought pipe is shown in the fol-
lowing table.

Size of pipe Capacity per

diam. in inched linear foot

1 0.1408 gallons

VA 0.0638

VA 0.0918

2 0.1632

2y2 0.2550

3 0.3672

4 0.6528

5 1.0200

6 1.4690

Pressure Systems. — Water in an open
kettle cannot be heated above 212 degrees at
sea level. At that temperature it boils and
all further heat energy is expended in vapor-
izing the water. In an open hot-water heat-
ing system the same is true, except that the

184

GREENHOUSES

slight pressure of the column of water in the
system may permit the water in the boiler to
reach a temperature slightly above 212 de-
grees. If water can be kept under pressure it
may be raised to almost any desired tempera-
ture, and in a heating system this would mean
less necessary radiating surface. The boil-
ing point of water under various pressures
above normal or atmospheric pressures is
shown in the following table:

Pounds pressure
Normal

Boiling point
.212.0° Fahr.

1
2
3
4
5
6
10

pound 2137°

" 215.3°

" 218.5°

221.5°

" 224.4°

" 227.1°

: 229.7°

" 240.0°

Several systems have been evolved to pro-
duce pressure in a heating system. One of
the earliest was the closed tank system in
which the expansion tank was made air-tight
and fitted with a safety valve set so as to let
the air in the tank escape at a certain pres-
sure. By this means the water in the coils
may be made to reach a temperature con-
siderably above the boiling point.

HOT WATER INSTALLATION

185

Recently various automatic devices using
a column of mercury to produce the same re-
sult have been placed on the market. One
model is designed to be placed in the pipe
leading from the return pipe to the expansion
tank, the tank in this case being open. The
advantage of these devices over the closed
tank system lies in the fact that they are
less likely to become clogged and stick than
are the safety or pop valves.

In action these so-called
^'generators" operate as
follows: The pressure is
determined by the height
of the column of mercury-
When there is no heat in
the boiler the mercury is
in the position shown at a,
Fig. 98. As soon as the
water becomes warm it ex-
pands and flows in through
the opening x. This forces

the mercury down in the
cistern and up through the
small pipe b. The amount
of mercurv is so arrano^ed
that when it is pushed
down to the level of the

Fig. 98.— A
of mercury
crator"

type
'gen-

186 GREENHOUSES

curve in the outlet pipe at c it overflows at d.
This allows some of the water to escape, and
this goes up through the pipe e to the ex-
pansion tank, but the mercury being heavier
falls back again through f to the cistern.

This automatically keeps the pressure at
any predetermined point, usually about lo
pounds, which makes possible the heating of
the water to a temperature of 240 degrees.
This makes practical the heating of the coils
to a high temperature in severe winter
weather and at the same time permits the
system to be run at lower temperatures in
mild weather. In this respect it has the ad-
vantage over steam. It is claimed for these
mercury "generator" devices that they
greatly improve the circulation of the water
in a heating system.

The most apparent advantage is that they
make possible the use of less radiating sur-
face, hence the first cost is less. It is but
fair to say that, as a rule, growers who have
installed them have found them satisfactory.
When the hot water is circulated by
pumps it is possible, though probably not de-
sirable to maintain a high pressure. Econ-
omy in heating by hot water lies in having
abundant radiating surface and rapid circu-

HOT WATER INSTALLATION 187

lation and then keeping the water at a mod-
erate temperature.

Caution. — In any system see that the ex-
pansion tank and the pipe leading to it are
placed where they will not freeze. As there
is ordinarily no circulation in the water they
contain they will freeze if placed where the
temperature falls below freezing. The re-
sults will almost surely be disastrous.

CHAPTER XII
STEAM INSTALLATION*

General Principles. — In steam heating
there is no circulation in the same sense that
there is in hot water heating, but the steam
is conducted into the heating coils,, where it
condenses. In condensing it gives up its
"latent'' heat. The water of condensation,
which occupies only about 0.017 part of the
space occupied by the steam, finds its way
back to the boiler either by flowing back
through the supply pipes, or through return
pipes connected with the opposite ends of the
coils. The latter system is most commonly
used in greenhouse heating.

In contrasting steam and hot-water heat-
ing it is well to keep in mind the fact that
only 180 B. T. U. are required to raise one

*In order to avoid repetition steam- heating is- discussed
largely in contrast to hot water 'heating, as described
in the preceding chapter. Both chapters should be
read by one wishing to inform himself on steam
heating.

188

STEAM INSTALLATION 189

pound of water from 32 to 212 degrees but
that 966 B. T. U. (usually considered as 1000)
are required to change a pound of water at
212 degrees into steam. When the steam is
condensed in the coils it gives off this heat.
This is known as the latent heat of steam. It
may be defined as the amount of heat ab-
sorbed in changing from a liquid to a vapor

or the amount given off in changing from a
vapor to a liquid state.

The problem in steam heating is to supply
an amount of radiating surface sufficient to
condense enough steam to furnish the
amount of heat required. Under ordinary
greenhouse conditions a square foot of steam
radiating surface may be counted on to con-
dense approximately one quarter pound of
steam per, hour. Each square foot of radi-
ating surface will, therefore, provide a fourth
of 960 or approximately 240 B. T. U. per
hour.

The number of B. T. U. required per hour
to heat a given house (see page 172), divided
by 240 will give, therefore, the number of
square feet of steam radiation required, and
from the table on page 174 the number of
linear feet of pipe may be easily determined.
Assuming a steam pressure of five pounds

190 GREENHOUSES

per square inch the following rule will be
found useful in determining the amount of
steam radiation required for a house when
the lowest outside temperature to be ex-
pected is not lower than zero.

Divide the num'ber of square feet of glass
and equivalent glass.

By 9 to heat house to 40 degrees

By 7 to heat house to 50 degrees

By 6 to heat house to 60 degrees

By 5 to heat house to 70' degrees

The quotient will" be the number of square feet of
radiating surface required

Size and Length of Coils. — -There is less
friction in steam than in hot-water heating,
and for this reason smaller pipes may be used
in the heating coils. They are seldom larger
than 1%-inch, and i%-inch is very commonly
used. Even i-inch pipe may be used in
comparatively short runs. Smaller pipes
may also be used in steam than in hot-water
heating, for the rjeason that the radiation per
square foot of surface is greater and there-
fore less surface is required. In other words,
an equal number of smaller pipes or a small-
er number of pipes of equal size may be used
in steam than in hot-water heating. Small
pipes furnish a greater amount of radiation
in comparison to their cubic capacity than

STEAM INSTALLATION

191

do large pipes. Large cast-iron pipes are
almost never used in steam heating.

When i-inch pipe is employed coils may be
safely used up to 75 feet in length; ij4-
inch up to 150 feet; and i>^-inch up to 250
feet. As with hot water, better results and a
more uniform temperature may be secured
by using two or more comparatively short
coils, rather than one which is excessively
long. In small houses it is possible to run
the coils entirely around the house, maintain-
ing an even downward slope.

Arrangement of Coils. — As indicated in a
preceding paragraph, either of two methods
of piping may be used. In one the water
resulting from the condensation of the steam

Fig. 99. — A corner coil. It allows for expansion of the

pipes

19'2

GREENHOUSES

flows back to the boiler through the supply
pipe. In this case all pipes have an upward
slope from the boiler, with no sags or pock-
ets in which the water can collect. This
method, sometimes known as the single pipe
system, is very commonly used in heating
dwellings where the pipes are mostly verti-

Fig. 100. — A mortise coil designed to allow for expan-
sion of pipes

cal, but in greenhouses having long, nearly
horizontal coils there is likely to be much
hammering in the pipes, caused by the in-
terference of the steam with the return
water.

A more satisfactory method for green-
house heating is to arrange the pipes much
the same as in hot-water heating, pro-
portioning the size to the supply and re-

STEAM INSTALLATION 193

turn pipes according to directions given in
a following paragraph. This is known as
the tw^o-pipe system. The return pipe en-
ters the boiler below the surface of the water.
The coils should have a fall toward the boiler
of about I inch to 20 feet. It is not wise
to use the straight coils commonly used for
hot water in steam heating as they do not
allow for the unequal expansion of the pipes
when the steam is turned on quickly. In
steam heating special form of coils are com-
monly used among which are the corner coil
and mortise coil.

Size of Supply and Return Pipes. — Theo-
retically, the size of the flow and return pipes
in steam heating may be much smaller than
in hot-water heating. This is especially true
of the return pipe, since the water which it
carries occupies only 0.017 of the space oc-
cupied by the steam from which it is con-
densed. In practice, however, the flow or
supply pipe for steam is made nearly as large
as for hot water and the return pipe only
slightly smaller.

The following table shows the flow of
steam in pipes of different sizes at a pressure
at the boiler of approximately five pounds.

1»4 GREENHOUSES

Size of pipe

inches

2/2

3-/2

A-y,

Pounds of steam per hour

138

220

390

570

800

1000

1400

2200

3200

To find the size of supply pipe required it is
only necessary to determine the number of
pounds of steam condensed per hour by the
coils (approximately one-quarter pound for
every square foot of radiation) and from the
above table select the correct size.

The following table, adapted from Carpen-
ter, gives the size of supply and return pipes
recommended to be used in the two-pipe sys-
tem for different amounts of radiation,
when a pressure of not greater than five
pounds is used.

Sq. ft. of radiation
to be supplied Size of supply pipe Size return pipe

200 VA inch 1% inch

400 2 " VA

700 2-^ " 2

1000 3 " 2

1600 y/2 " 2A

2300 4 " 2A

3200 4-y2 " 2y2

STEAM INSTALLATION

195

4100

((

6500

9500

3/2

Valves. — In steam heating it is essential
that each coil be provided with a cut-off
valve. This is even more essential than with

Fig. 101. — Reducing valve

19G GREENHOUSES

hot water since with steam heating the tem-
perature of the steam must be at least 212
degrees, while with hot water the tempera-
ture may be varied according to the weather.
Automatic air valves are placed at the high-
est point of each coil and also in the supply
pipes.

High Pressure Heating. — When steam
above five pounds pressure is used it is known
as high pressure heating. For greenhouse
purposes high pressure heating is not satis-
factory, as the pipes are too hot. In
large establishments, however, a high press-
ure is often maintained at the boiler and is
passed through a reducing valve before it
enters the coils.

Vacuum and Vapor Systems. — Several
heating systems are now on the market which
endeavor to give to steam heating some of
the advantages claimed for hot water, viz., a
lower temperature of the heating pipes and
less frequent attention to the boiler. They
dififer from straight steam heating in that a
partial vacuum is maintained within the
system, thus causing the water in the boiler
to give off vapor at a temperature of less
than 212 degrees.

STEAM INSTALLATION 197

There are several different systems but
they may all be grouped roughly into three
classes: (i) Those in which a vacuum is
created by means of a pump or other me-
chanical device; (2) those in which the air
is expelled by raising the steam to a relative-
ly high pressure, and then preventing it from
returning by some form of automatic mer-
cury seal, and (3) those in which a constant,
though slight, vacuum or tendency to vac-
uum is maintained, by connecting the sys-
tem with the chimney and utilizing the "pull"
of the draft.

These systems are now being rapidly in-
stalled in public buildings and dwellings, and
no doubt will be found more satisfactory
than steam for greenhouses. In addition to
the advantages given above it is claimed for
these systems that they are more economical
of fuel than are either steam or hot water,
that the circulation is better and surer, and
also that there is no trouble arising in long
runs from water of condensation.

Arrangement of Boilers. — In the common
gravity system of steam heating the boilers
must be below the level of all mains and
coils. When thev cannot be so located,

198 GREENHOUSES

special devices to be described later must
be employed to return the water of conden-
sation. As with hot water, two or more
boilers should be provided, rather than one
large one, to allow for repairs in case of ac-
cident and for use in severe weather to avoid
the necessity of forcing.

Steam Pumps and Traps. — As suggested
in the preceding paragraph, it is sometimes
impossible or inconvenient to place the boil-
er below the level of the heating coils. This
is especially true in large establishments, re-
quiring large boilers using large quantities
of fuel. In order to return the water of con-
densation in such cases steam return traps
and steam pumps are used. Their use is al-
so necessary where a higher pressure is car-
ried at the boiler than in the coils.

The return trap is a contrivance which is
automatic in its action, and which overcomes
the back pressure from the boiler by an in-
genious method of equalizing the difference
in pressure between the boiler and the coils.
Being automatic in its action and requiring
but little attention it has been quite gener-
ally used. Steam pumps, on the other hand,
require considerable attention, though they

STEAM INSTALLATION

199

are less complicated than the return traps.
A small, separate boiler is generally used to
operate the pump, and the exhaust and sur-
plus steam is turned into the general heat-
ing system after being reduced to low pres-
sure. Gas and electric motors are also used
to drive the pumps for returning the water
of condensation.

Fig. 102. — A type of steam return trap

CHAPTER XIII
BOILERS, FUELS AND FLUES

The terms boiler and heater as used in dis-
cussing greenhouse heating systems are
synonymous. It is customary, however, to
speak of a steam heating apparatus as a
''boiler" and of a hot-water heating appar-
atus as a "heater," probably because in steam
heating the water boils, while in hot-water
heating it is not supposed to boil. It often
occurs, however, that the same kind of heat-
ing apparatus is used in both steam and hot-
water heating with no essential changes, ex-
cept in the accessories. In this chapter the
term boiler will be applied to both steam and
hot-water heating devices.

The boilers used in greenhouse heating
differ but little from those used in heating
other buildings. In fact the same makes
and styles of boilers are very frequently used
for both purposes. Certain manufacturers
have, however, made a thorough study of
greenhouse heating and have developed boil-

200

BOILERS, FUELS AND FLUES 201

ers with this particular end in view. In
buying a boiler the safe plan is to purchase
a style which has fully established itself on
the market and which is made by a thorough-
ly reliable firm. Such boilers will have passed
the experimental stage and repairs may be
secured quickly and reasonably.

Essentials of a Boiler. — The function of
the boiler is to extract the latent heat from
the fuel and transfer it to the water or steam,
which may be circulated when needed. The
essentials are, a grate on which the fuel is
burned and a watertight receptacle, so ar-
ranged as to present a large amount of sur-
face (known as fire surface) to the fire or
burning gases. The problem of the manu-
facturer is to so arrange and proportion the
fire surface and the grate surface that the
heat of the burnins: fuel mav be most econ-
omically absorbed and distributed.

Grate Surface. — For best results the
amount of grate surface should be large
enough, so that the fire will not have to be
forced. In small and medium-size boilers
the rate of combustion should not exceed
from five to seven pounds of coal per square
foot of grate per hour. In larger boilers the
rate of combustion of fuel mav be as hicrh as

202 GREENHOUSES

from six to ten pounds per square foot per
hour.

A pound of best coal has a heating value
of about 14,000 B. T. U. per pound, of which
only about 60 per cent, or 8,400 B. T. U. are
utilized in heating water or producing
steam. It is the usual practice to estimate
that each pound of coal will impart about
8,000 B. T. U. to the heating medium, and
that each square foot of grate surface will
burn about six pounds of coal per hour. This
gives 48,000 B. T. U. per square foot of grate
surface per hour.

To find the approximate number of square
feet of grate surface required to heat a given
house, find the number of heat units re-
quired, by the method described in Chapter
XI, and divide by 48,000.

In general, a square foot of grate surface
is sufficient to supply 250 square feet of
radiating surface.

Fire Surface. — Fire surface (sometimes
known as heating surface or water surface)
is of two kinds; direct and indirect. The
direct fire surface is that immediately above
or around the fire, against which the light
of the burning fuel shines. Indirect fire sur-
face is that which receives the heat from the

BOILERS, FUELS AND FLUES 203

burning gases on their way to the chimney.
Direct fire surface is three times as effective
as indirect. It does not follow, however,
that boilers having the greatest amount of
direct fire surface are the most efficient, for
there must be sufficient length of fire travel-
to consume the gases and enable them to give
up the greater part of the heat of combus-
tion to the water.

To be most effective the fire surface is so
arranged that the heat will impinge at right
angles against it. This is accomplished with-
out serious interference with the draft,
and without making the course of the water
in the boiler so long and tortuous as to in-
terfere with its rapid circulation. The pro-
portion of fire surface to grate surface dif-
fers so widely in the different forms of boil-
er construction that no definite rule can be
given. It may vary from 15 to 35 square
feet to each square foot of grate area.

Types of Boilers. — Broadly speaking,
there are three types of boilers, when classi-
fied as to their form of construction : ( i ) Boil-
ers in which the water is spread out in thin
sheets between layers of iron or steel and
against which the heat strikes; (2) tubular

204

GREENHOUSES

boilers in which the burning gases travel
through tubes or flues which are surrounded
by water; and (3) water-tube boilers in
which the water is contained in tubes about
which the burning gases circulate. Many

Fig. 103. — A type of ''vertical ' or
"square" sectional boiler

manufacturers combine two, and sometimes
all, of the above types in one boiler. The
two latter types are more commonly used
for power purposes than is the first, but for
heating establishments of moderate size a
modification of the first is widely used.

BOILERS, FUELS AND FLUES

205

Cast and Wrought-Iron Boilers. — The
cast-iron boiler has a size limit above which
it is impracticable to go, though two or more
may be joined in a series. It is also claimed
that on account of the thickness of the walls

Fig. 104. — End view of "square" sectional

boiler showing fire travel. A and B, push

nipples for joining sections

it is less economical of fuel than are wrought-
iron boilers, which have thinner walls. On
the other hand, cast-iron boilers do not rust
as badly as wrought-iron ones when not in
use, and they have no flues to be burned out
by the sulphurous gases resulting from the

206

GREENHOUSES

use of the poorer grades of coal. But they do
sometimes crack, and they have a disgusting
way of doing it at the most inopportune
moment.

Fig. 105. — Side view of "square" sectional boiler
showing fire travel

Where fuel is cheap and abundant, and
especially in small ranges, or where the boiler
is in a damp basement and likely to be neg-
lected during the summer, cast-iron boilers
are likely to give better satisfaction than
wrought-iron. In large establishments of
100,000 feet or over, large wrought-iron tubu-

BOILERS, FUELS AND FLUES

207

208

GREENHOUSES

lar or water-tube boilers are almost always
used.

Styles of Cast-iron Boilers. — There are
three general types or styles of cast-iron
boilers. The most popular is the "vertical" or

''square"sectional boil-
er. The advantages
claimed for these forms
of boilers are: (i)
They may be enlarged
by adding extra sec-
tions; (2) a break or
crack will usually be
confined to one sec-
tion; and (3) they may
be made in large sizes
because the individual
castings are compara-
tively small and light.
The sections are joined
together by accurate-
ly ground push nip-
ples or by screw nipples. Probably 80 per
cent, of the cast-iron boilers now being
placed in greenhouses of moderate size are
of this general type-

A second style of cast-iron boiler is
known as "horizontal" or "round" sectional
boiler. It gives good satisfaction in small

Fig. 107.— A type of

"round" or "horizontal"

sectional boiler

BOILERS, FUELS AND FLUES

209

ranges but is not made in large sizes. In
a third style there are no sections, but the
boiler proper is cast in one piece. For this
reason its size is limited. It is also open
to the disadvantage that a crack will spoil
the whole boiler. It is little used at present.

Fig. 108. — Corrugated fire box •boiler. The boiler
proper is of a single casting

Styles of Wrought-Iron Boilers. — Most
wrought-iron boilers are either tubular or
water-tube in construction, though the tubes
or flues are sometimes connected with cast-
iron headers. A new type of wrought-iron
boiler is now being extensively advertised for
greenhouse heating. It is claimed for this
type that it steams more quickly than the

210

GREENHOUSES

i'ig. 1U9. — Type of tubular boiler much used in green-
house heating

tubular boilers and that it is much more dur-
able. As a rule users seem to be well satis-
fied with it.

Steam and Hot-water Boilers. — As usually
constructed, low-pressure steam boilers dif-
fer but little in construction from hot water
boilers. The essential difference is that in
steam boilers provision is made for a steam
chest or storage above the water line, while
in hot-water boilers the space between the
top of the tubes and the top of the boiler is
so small that there is no room for an adequate
steam storage. This is equivalent to saying

BOILERS, FUELS AND FLUES

211

Fig. 110. — Battery of two marine type boilers used for
greenhouse heating

that a steam boiler may be used for hot-water
heating, but that a hot-water boiler is rare-
ly satisfactory for steam heating. Large
steam boilers are quite frequently used in
hot-water heating when equipped with the
necessary fittings which are described in
a succeeding paragraph.

Boilers for Soft and Hard Coal. — Hard coal
burns with a ''short" flame, and much less
fire travel is required to burn the gases than
when soft coal, which burns with a ''long"
flame, is used. More flue way is also re-
quired for soft coal and the grates are more
open. Most greenhouse boilers which are

212

GREENHOUSES

designed for soft coal will burn hard coal
equally well. If they are designed primarily
for hard coal they will not burn soft coal
efficiently. More grate surface is required
for soft coal than for hard coal, because it is

Fig. 111. — Wrought-iron boiler without flues

more bulky weight for weight. Most mod-
ern greenhouse boilers will burn either hard
or soft coal, but a larger size will be required
for soft coal than for anthracite.

Boiler Ratings. — An approximate idea of
the size of boiler needed may be found by
figuring the amount of grate surface by the
method described on page 202. Boiler manu-

BOILERS, FUELS AND FLUES

213

facturers, however, rate their boilers show-
ing their capacity. Some give the number
of square feet of glass that they will heat to
a given temperature; others give the number

Fig. 112. — Sectional view of boiler shown in Fig. Ill

of linear feet of radiating pipe of a given
size which they will supply ; and still others,
especially the manufacturers of large tubu-
lar boilers, give the capacity of their boilers
in terms of horse-power.

Since different manufacturers often ques-
tion the correctness of the ratings of their

214 GREENHOUSES

competitors, it is but fair that buyers
should be recommended to exercise consider-
able caution. Probably most boilers will,
under favorable conditions, develop the num-
ber of heat units for which they are rated,
but for the sake of safety and to prevent the
necessity of forcing, it is best to select boil-
ers with ratings at least 20 per cent, in ex-
cess of the theoretical needs.

When boilers are rated according to the
number of linear feet of radiating pipe they
will supply, it is usually given in terms of
either 3%-inch cast-iron pipe or in 2-inch
wrought-iron pipe. The following table
gives the length of pipes of other sizes equiv-
alent to I linear foot of 2 and 31/2-inch pipe.

1 ft. of 3-^4 in. C.I/ pipe equals.. 3.04 ft. 1
1 ft. of 3^ in. C.I. pipe equals.. 2.41 ft. VA
1 ft. of 3-^ in. C.I. pipe equals.. 2.10 ft. V/2
1 ft. of 3^ in. C.I. pipe equals.. 1.68 ft. 2
1 ft. of 3-^ in. C.r. pipe equals. .1.39 ft. 25^
1 ft. of 2 in. W.I. pipe equahr. .1.806 ft. 1
1 ft. of 2 in. W.l. pipe equals. .1.431 ft. VA
1 ft. of 2 in. W.I. pipe equals. .1.25 ft. VA

n. W.I. pipe
n. W.I. pipe
n. W.I. pipe
n. W.I. pipe
n. W.I. pipe
n. W.I. pipe
n. W.I. pipe
n. W. I. pipe

Most boiler ratings are given for a mini-
mum outside temperature of zero degrees,
Fahrenheit. For localities subject to a tem-
perature of 10 degrees below zero a boiler
of 10 per cent, greater capacity should be se-

BOILERS, FUELS AND FLUES

215

cured, and for localities subject to a tem-
perature of 20 degrees below zero, a boiler of
20 per cent, greater capacity should be se-
cured.

The term horse-power, as applied to boil-
ers, represents the energy developed in evap-
orating 34.5 pounds of water per hour from
a. temperature of 212 degrees, or the develop-
ment of 33,317 B. T. U. per hour. Roughly,
a heating boiler will supply 100 square feet
of radiation for each horse-power which it
develops.

Fig. 113. — Altitude giiage for hot
water boiler

Boiler Accessories. — It has already been
stated that a steam boiler may be used for
hot-water heating by simply changing the
fittings. When used for hot-water heating

216

GREENHOUSES

the boiler is fitted with an altitude gauge,
which shows the height of the water in the
system; also with a thermometer to show the
temperature of the water. A valve is pro-
vided for draining the boiler and, if desired,
an automatic damper regulating device may
be installed.

When used for steam
heating the boiler is only
partially filled with water,
and a water column and
guage is necessary to indi-
cate the height of the
water. A steam guage is
also necessary to indicate
the pressure; and a safety
valve to automatically re-
lieve the pressure, if it be-
comes too great for safety.
Steam boilers are usually

Fig. 114.— Water col- .... ^ 7

umn and guage for equipped With automatic
steam boilers hamper regulators. They
are rather more efiicient than the regulators
used on hot-water boilers. A drainage valve
is provided the same as for hot-water boil-
ers. Many states require that all steam boil-
ers be equipped with a fusible plug, which is
simply a brass plug with a tin core, which

BOILERS, FUELS AND FLUES 217

Fig. 115. — Steam guage

is screwed into a hole in the boiler near
the bottom. If the water level falls below
the plug the heat melts it out, thus making

Fig. 116. — Diagram of automatic damper regulator. The
steam pressure acts against a flexible diaphram which
is connected with the dampers by means of a lever and

chain

218

GREENHOUSES

an opening and lessening the danger of an
explosion.

The boiler and all pipes, except those in
the greenhouse itself, should be insulated as
much as possible to prevent loss of heat. The
best known material for this purpose is as-
bestos. For coating boilers it may be had
in a granular form, which is mixed with
water and applied with a trowel or the bare
hands. For covering pipes molded casings
may be had to fit all sizes of pipe.

Fig. 117. — Asbestos pipe covering

FUELS

Coal is used almost universally for fuel in
greenhouse heating, except in sections where
natural gas or oil are cheap and abundant.
Gas is an ideal fuel, but somewhat treach-
erous inasmuch as the pressure is likely to be
lowest in the coldest weather. Care should
be taken to see that there are no leaks, as it
is very explosive, and it is also poisonous to
vegetable as well as animal life.

Broadly speaking, coal is of two kinds,

BOILERS, FUELS AND FLUES

219

anthracite or hard coal, and bituminous or
soft coal. Hard coal burns with little smoke

Fig. 118. — Boiler etiuipped for using natural gas

and IS much heavier than soft coal, although
it may not develop as much heat per ton.

220 GREENHOUSES

It is easier and cleaner to handle, and re-
quires less attention in firing, but in most
sections is more expensive.

Soft coals are of two general types; The
free burning and the coking. The latter
fuses together in burning and is somewhat
more difiicult to handle in the furnace than
the free burning, though it is preferred by
some firemen.

The heating value of a coal depends upon
the percentage of total combustible matter
contained, and upon the heating value per
pound of the combustible portion. In some
semi-bituminous coals the heating value runs
as high as 15,750 B. T. U. per pound. The
heating value of a few common types of
coals as given by Kent are shown in the fol-
lowing table.

Kind of coal B.T.U. Kind of coal B.T.U.

Anthracite Cambria Co., Pa. . . . 14450

Northern Coal field ..13160 Somerset Co., Pa. ...14200

East Middle field ...13420 Cumberland, Md 14400

W^est Middle field ...12840 Pocahontas, Va 15070

Southern field 13220 Brier Hill, 0 13010

Scott Co., Tenn 13700

Semi-'bituminous Big Muddy, 111 12420

Clearfield Co., Pa. ...14950 Missouri 12230

Soft coal is more commonly used in green-
houses than is hard coal. This js especially

BOILERS, FUELS AND FLUES 221

true in large establishments. The price
varies with the quality, distance from the
mines, etc.

The average cost for soft coal to 6i grow-
ers, living east of the Mississippi River, for
the season of 1911-12, was $2.33 per ton. The
average amount used for the season was 11.6
tons for each 1,000 square feet under glass.

Underfed Boilers. — The term "underfed"
is applied to a method of stoking, in which
the coal is fed from the bottom instead of
the top of the furnace. It is claimed for
this system that it insures a more perfect
combustion and that cheaper grades of coal
may be used. Boilers employing this prin-
ciple have not come into very general use in
greenhouse heating, probably because they
will not handle successfully all grades of
coal.

Self-stoking Boilers. — Stoking devices are
practical only in large establishments us-
ing large boilers. There are several types,
some of which work on practically the same
principle as the underfed furnaces mentioned
above, except that their action is automatic.
In other forms the grate bars are arranged
in the form of an endless chain, which is

222 GREENHOUSES

moved slowly from the front to the rear
of the fire-box by means of gearing. It is
claimed for the self-stoking devices that they
not only save labor, but that they are more
economical in the use of fuel than is hand
stoking.

Points to Consider. — The following points
should be kept in mind in selecting a green-
house heating boiler:

1. It should be of ample size — at least one
size larger than is theoretically necessary.

2. The fire-box should be deep and spac-
ious. This is especially true of boilers for
small establishments where a regular fire-
man is not employed.

3. The combustion chamber (the chamber
above the grate) should be large enough to
insure thorough combustion of the gases.

4. The boiler should be so arranged that
it may be easily cleaned, especially the flues
and heating surfaces.

5. The grates should be heavy but easy
to operate and easily removable, so that re-
pairs may be made quickly.

6. The water travel should not be so cir-
cuitous as to prevent of rapid circulation.

7. There should be no packed joints. All

BOILERS, FUELS AND FLUES 223

unions should be made with push or screw
nipples.

8. Soft coal burners require a somewhat
different construction than do hard coal burn-
ers. The kind of fuel to be burned should
be clearly in mind when selecting a boiler.

9. The ash pit should be deep and com-
modious. Shallow ash pits are likely to be-
come filled so that the draft is impaired
and the grate bars ruined.

CHIMNEYS AND FLUES
A very essential part. of the heating equip-
ment is the chimney or flue. Its purpose is
twofold: First, to create a draft in order
to furnish air to promote combustion; and
second, to carry off smoke and gas. The
size and height of the chimney required de-
pends on the size of the grate surface. Mere
velocity does not- necessarily indicate that
the draft is sufficient; the chimney must be
of sufficient size to carry the required
quantity.

The velocity of the gas in the flue depends
on the height of the flue and upon the tem-
perature of the gas. The difference be-
tween the weight of the hot gases in the
chimney, and a column of cold air of equal

224

GREENHOUSES

size outside creates a flow upward in the
chimney. This difference increases with the
height of the chimney, and if the difference
in temperature increases the velocity is more
rapid. Locations high above sea level require
higher chimneys than those near sea level,
on account of the rarety of the atmo-

Fig. 119. — Chimneys should extend above the roofs of
adjacent buildings

Sphere. For example, at Denver, Col., (5,300
feet) the height should be about 20 per cent,
greater than at sea level.

Chimneys should be vertical if possible and
the inside should be smooth and free from all
obstructions. They should also extend well
above the roofs of adjacent buildings, particu-
larly when there is danger of a "down
draft." Round chimneys present less sur-
face per cubic capacity than do square chim-
neys, and are thus more efficient. For the
same reason square flues are better than ob-
long flues.

BOILERS, FUELS AND FLUES 225

The following table shows the size and
height of chimneys required by steam boil-
ers. For hot-water boilers multiply the radi-
ating surface by 1.5.

Height of chimney in feet

Sq.ft.

f
20

100

120

st'm rad

Size of Chimney

(dia.

or 1 sid

e sq.)

in inch

250

7.4

7.0

6.7

6.4

6.2

6.0

500

9.6

9.2

8.8

8.2

8.0

6.6

7.3

7.0

750

11.3

10.8

10.2

9.6

9.3

8.8

8.5

8.2

1000

12.8

12.0

11.4

10.8

10.5

10.0

9.5

9.2

1500

15.2

14.4

13.4

12.8

12.4

11.5

11.2

10.8

2000

17.2

16.8

15.2

14.5

14.0

13.2

12.6

12.1

3000

20.6

18.5

18.2

17.2

16.2

15.8

14.4

4000

23.6

22.2

20.8

19.6

19.0

17.8

17.0

16.3

5000

26.0

24.6

23.0

21.6

21.0

19.4

18.6

18.0

6000

28.4

26.8

25.0

23.4

22.8

21.2

20.2

19.5

7000

30.4

28.8

27.0

25.5

24.4

23.0

21.6

20.8

8O0O

32.4

30.6

28.6

26.8

26.0

24.2

23.4

22.2

9000

34.0

32.4

30.4

28.4

27.4

2S.6

24.4

23.4

10000

27.0

34.0

32.0

34.0

28.6

27.0

25.4

24.6

15000

■ • •

• • .

38.4

36.2

35.0

33.0

31.0

29.2

20000

• • •

43.0

42.0

41.0

37.0

35.0

34.0

30000

.. .

50.0

48.0

46:0

43.0

41.0

CHAPTER XIV
WATER SUPPLY AND IRRIGATION

An abundant supply of water at a reason-
able cost is necessary for the successful op-
eration of a commercial range of green-
houses. Figures compiled from the experi-
ence of several growers show that the con-
sumption of water by a vegetable crop in a
greenhouse during the bright, hot days of
June and July may be as high as 280 gallons
per day per 1000 square feet of crops. As
the watering is done over a period of not
more than three or four hours per day, it is
necessary to make arrangements to supply
the maximum amount needed during that
length of .time, rather than during the 24
hours of the day as is usually figured for
domestic purposes.

When city water is available at a reason-
able price it is doubtful if it will pay the
small grower to go to the expense of pro-
viding a private supply. Sometimes, how-
ever, the conditions are such that a private

226

IRRIGATION

227

supply of water may be had at small expense
from springs, ponds or streams. In larger
establishments it may be cheaper to install a
private system than to depend on city water.
Often, also, the ranges ar^ located out-
side the city limits where city water can-
not be had. Data based on the reports of

nearly lOO florists and
vegetable growers
show that the average
cost per I, GOO gallons
of city water is i8
cents, and that the
average cost of the
home supply, includ-
ing cost of equipment,
depreciation and main-
tenance, is 21 cents
per I, GOO gallons.

Pumps. — For gen-
eral purposes some of
the many types of
combination lift and
force pumps now on
the market are com-
monly used. Pumps

of this type may be had which are directly
geared to a gas or steam engine, or to an

Fig. 120. — Pumping- jack

for applying power to a

hand pump

228

GREENHOUSES

MANHOLE

^5 I I S ^ ^

COMPHESS^D
AIR

electric motor. Usually, a hand pump of
large size is used, and power is applied by
means of a pumping jack.

A very efficient but somewhat delicate
pumping device is the combined hot-air-
engine and pump.
These pumps give
very good satisfac-
tion where the water
is reasonably close
to the surface, or
when it does not
have to be pumped
against too great a
pressure. Improved
types of large size
are now available,
and are verv econ-
omical of fuel, but
the engine is not as
well adapted for
general power pur-
poses as are gas en-
gines.

A form of pump, which is becoming quite
popular for domestic use is the auto-pneu-
matic pump. It is designed to be used in
an open well or a cased well of large bore,
as the pump proper is placed entirely be-

kYSlL CAS f A/ a

ZOW ir/Ar£ff i£ysi.

IA/C/f£AS£.'7
3/4f"^/^£

■AUTO -fN£aMAT/e

Fig. 121. — Diagram showing
installation of an auto-
pneumatic pump

IRRIGATION 229

neath the water. It is operated by com-
pressed air, hence an air pump and an air
tank are required. Its chief advantage for
domestic purposes lies in the fact that it
starts automatically when the faucet is
opened, thus giving a supply of cold water
direct fr.om the well. For greenhouse pur-
poses this is a disadvantage, as the water may
be too cold to use on the plants.

Pump cylinders should not be more than
20 feet above the surface of the water, as this
is the limit of practical suction. When the
water is more than 20 feet below the surface
the pumping cylinders are lowered accord-
ingly. In deep wells it is common to lower
the pumping cylinders well into the water.

Capacity of Pumps. — The capacity of a
pump depends upon the size of the cylinder
and the length and rapidity of the strokes.
The table on page 230 gives the discharge per
stroke in gallons, of pumps having cylinders
of various sizes. This, multiplied by the
number of strokes per minute, will give the
capacity per minute.

Power Required. — The power required to
operate a given pump may be determined as
follows: Multiply the number of gallons
pumped per minute by 8.337 pounds (the

230 GREENHOUSES

1— (

T— <

1— (

T— I

1— (

T-(

1— <

1-H

T— I

Ti-

»— (

""i-

1 — I

y—t

1 — 1

1— (

est

T— (

T— 1

Tt;

r>j

Tt;

'— '

y—t

T— (

Cli

»— (

vo
CO

CO
eg

"rt

T— (

1— I

PL|

rt-

'■^

v-H

»— (

T— (

■^

U-)

»— (

CNl

1—1

1— (

4->

■J-J

<V1

T— I

>-<

t>.

»— (

1— (

»— (

tNj

1—1

1— t

4-1

■♦-»

1— 1

T— (

»— 1

I-]

Tj-

T— 1

t>^

y—t

r— I

<S{

r>»

»-i

y—\

y—i

T— (

CNJ

In.

Tf-

Tj-

1— 1

y—t

r— 1

1— (

1> J_ C/5 SIN \(N \(V) \(N

-<-' (D ID M\ H-\ v-\ ^

2:J-o^ rgegcocoTfTttotoNo

£ C JrJ

Q C^

IRRIGATION 231

weight of a gallon of water). This will give
the weight pumped per minute. Multiply
this by the total lift in feet. This will give
the number of foot-pounds of energy required
per minute. Divide this by 33,000 (the num-
ber of foot-pounds in a horse-power) and the
result will be the number, of horse-power re-
quired. Pumping outfits are only about 50
per cent, efficient, so that the results ob-
tained by the above are doubled in actual
practice. On the average one horse-power
will pump 30 gallons per minute to the height
of 100 feet. In pumping water against press-
ure in a pneumatic tank, extra power will
be required. Extra power will also be re-
quired when the waten is pumped for any
considerable distance, on account of the fric-
tion of the pipes. The frictional loss in feet
of lift for each 100 feet of pipe of various
sizes is shown in the following table.

allons

Size

of Pipe

;r min.

^ in.

lin.

P4in.

13^ in.

2 in.

2V2 ir

Frictional

Loss

29.9

1.Z

1.4

1.0

0.28

0.09

66.0

16.1

5.5

2.2

0.57

0.18

115.0

28.0

9.5

4.8

0.96

032

179.0

43.7

14.7

6.0

1.7

0.48

264.0

63.2

21.0

8.6

2.1

0.69

372.0

85.1

28.9

11.6

2.7

0.92

461.0

110.0

37.0

14.9

Z.l

1.2

232

GREENHOUSES

This loss by friction cannot be disregarded.
Suppose, for example, it is desired to deliver
20 gallons per minute at a distance of 100
feet. By referring to the above table it will
be seen that if a ^4-inch pipe were used, a
loss equal to a head of 115 feet would be
sustained, while if a iy2-inch pipe were used
a loss of only 4.8 feet would be sustained.
It is economy to use pipe of generous size.

Hydraulic Rams. — The hydraulic ram is
a device which utilizes the force of water.

Fig. 122. — A simple type of hydraulic ram. a, intake
pipe; f, delivery pipe

IRRIGATION

233

falling a short distance, to elevate a portion
of the water to a greater height. It is
wasteful of water, but when a never-failing
stream of sufficient flow and fall is avail-
able it is one of the most economical and
satisfactory of water-lifting machines.

Rams are somewhat difficult to install by
a novice, because of the rather exacting con-

'"^^

rtfw*r/o« ^etr

k Livim cMri vNtvft

Fig. 123. — Plan for installing a hydraulic ram

ditions necessary to secure the most efficient
service. When they are properly installed,
however, they give little trouble, provided
they are kept from freezing.

Capacity of Rams. — To find the capacity
of a ram for any given conditions proceed as
follows : Multiply the fall in feet by the quan-
tity of v/ater which may be supplied to the
ram in gallons per minute, and divide the
product by the height the water is to be
raised. The result will be the number of
gallons delivered per minute. The above

234 GREENHOUSES

disregards loss by friction and assumes that a
ram of the proper size is installed.

By use of the table on page 235 an estimate
of the capacity of a ram for different con-
ditions may be determined. The left-hand
column indicates the number of feet of fall
possible to secure, and the numbers at the top
of the vertical columns indicate the height
to which water is to be raised.

For example: Suppose we have a stream
with a flow of 100 gallons per minute; that
there is an available fall of 10 feet, and that
it is desired to raise the water 40 feet. The
factor in this case (252) will be found in the
column headed by 40 and opposite the num-
ber 10 under power head. Multiplying 252
by 100, we have 25,200, the number of gal-
lons that may be delivered per day by a ram
of the correct size.

In ordering a hydraulic ram the following
information should be given:

1. Flow of water in gallons per minute.

2. Vertical fall in feet.

3. Distance in which fall is obtained.

4. Vertical height above ram the water
is to be raised.

5. Distance water is to be forced.

6. Number of gallons required per day.

IRRIGATION 23.J

JZ; -^ fOrhiOVOvOt^COO'— ((M-rl-iOvooOOO

Q f^ orO'^voooO'too<»^0'^cocoThi/-)

r^VO OOC\i-HC-l^voONCgiOOrot^Or^O'^

I— I

??C5 vo>j^Tj-Tfcor<ioofooo"^o

K^ i-tl— ti— I,— (,— ((MCvlCOfOTl-Tj-lO

O ho

0.0 O^l-oOC^'OCVl'-ifCC-l'OO

•^ c!-5- CNTfvoONi-HiOOiOfoOOTf

p ^^ CVl CO CN-5 rl- rt lO

(J '^fOTj-lO---

W ^c?

»j^vot^ooa\or<jrtvoooo<NTf050o

To use: Multiply the factor opposite power head and under
pumping head by the number of gallons of water avail-
able per minute. The product will be the number of
gallons delivered per day. ^See page 234.)

236 GREENHOUSES

Double-acting rams which will utilize the
water from a creek or river as power and
pump water from a spring or shallow well
may be had, but they are somewhat more
complicated.

Windmills for Pumping. — The chief ob-
jection to the windmill for pumping is its lack
of dependability. Where the wind is fairly
constant, or when a large storage capacity
may be had cheaply, windmills are the cheap-
est source of power. On the average the
windmills used for pumping develop about
three-fourths horse-power. The geared steel
wheel mills are more efficient and will run
in lighter winds than will the wood wheel
mills.

Storage Tanks. — Storage tanks are neces-
sary with most water systems, to insure a
constant supply and to furnish pressure.
They fall naturally under two heads: (i)
Open tanks in which pressure is obtained by
gravity; (2) closed tanks, usually pneumatic
tanks, containing air into which water is
forced, the compressed air in this case furn-
ishing the desired pressure.

In placing tanks in the attic, or other ele-
vated positions, it is well to keep in mind the

IRRIGATION 237

weight of water and to see that the supports
are amply strong. For example, a lo-barrel
tank of water will weigh, in addition to the
tank itself, more than one and a quarter
tons.

The pressure to be obtained from elevated
tanks depends upon their elevation, each ad-
ditional foot giving a pressure of about 0.433
pounds per square inch. The following table
shows the pressure (disregarding friction)
to be obtained at various heights.

Height in feet Pressure per sq. inch

10 4.33 pounds

20 8.66

30 12.99

40 17.32

50 21.65

60 25.98

70 30.31

80 34.64

90 38.97

The advantage of the pneumatic tank lies
in the fact that it may be placed in any out-
of-the-way place in the basement, or it may
be buried in the ground below the frost line.
There is little danger in its use if it is pro-
vided with a pressure gauge and safety valve.

Capacity of Storage Tanks. — The capac-
ity of storage tanks is not difficult to arrive
at by simple mathematics, unless they are

238 GREENHOUSES

of unusual shapes. For convenience, tables
are given below showing the capacity of
round and square tanks of standard sizes.
When pneumatic tanks are used, about a
third of their capacity is occupied by the
compressed air.

TABLE SHOWING CAPACITY OF ROUND
STORAGE TANKS

Diameter Height Capacity Diameter Height Capacity
Eeet Eeet Gallons Eeet Eeet Gallons

378

735

470

5/2.

1400

567

423

756

528

440

635

588

845

5 5 735 6 5 1056

TABLE SHOWING CAPACITY OF RECTANGULAR

TANKS

Width Height Length Capacity

Feet

Gallon

2/2

378

360

448

2/2

565

(>JZ

478

598

2/2

748

718

IRRIGATION

239

o
U

b£

':c

240

GREENHOUSES

IRRIGATION
There are two general methods of water-
ing greenhouse crops aside from hand water-
ing. One is by an overhead sprinkling sys-
tem; the other is by an underground or sub-
irrigating system. Of these the overhead
system is by far the more popu-
lar. A census of a large number
of growers of greenhouse vege-
tables shows that practically 75
per cent, use some form of over-
head irrigation, while only two
out of the whole number con-
sulted were using sub-irrigation.
Practically the only system of
overhead irrigation used in
greenhouses is one in which
pipes, fitted with nozzles which
Fig. 125 — A throw a rain-like spray, are run

type of nozzle . ,. . r ^i t j

used in over- lengthwise of the house and so
head irrigation arranged that they may be rotat-
ed to throw the spray on both sides of the pipe
line. The original system is known as the
Skinner system, but there are others now
on the market. Pipe lines for this system
should be about 16 feet apart and as far from
the foliage as possible. The nozzles should
be 3 feet apart. This system will operate

IRRIGATION

241

satisfactorily on a' water pressure of from
10 to 30 pounds.

When constructing benches for sub-irriga-

-A

Fig. 126. — Greenhouse bench arranged for sub-irrigation.
A, cement troughs on bottom of bench; B, drain tile or
perforated pipes for supplying water; C, drainage spaces
between troughs.

tion, the essentials are a water-tight bottom,
usually of cement, to prevent the water from
leaking through, and perforated pipes or tiles
for distributing it along the bench. This
system has been tried out extensively with
varying results by the Ohio experiment
station.

CHAPTER XV
CONCRETE CONSTRUCTION

Concrete is a combination of Portland
cement, sand, crushed stone or gravel and
water, thoroughly mixed and then allowed
to set or harden.

Portland cement, or cement, as it is now
commonly known, is manufactured by burn-
ing and grinding together limestone and
clay, or shale, in certain proportions. It de-
rives its name, Portland cement, from its re-
semblance to Portland stone. It is also
sometimes known as hydraulic cement, or
building cement.

Concrete has wellnigh revolutionized
building practice in the last 25 years, but in
no case has it displaced masonry to a greater
extent than in greenhouse construction.
Formerly, the walls of a greenhouse were a
source of much trouble, because of their
rapid deterioration, but it was soon found
that when conc'rete was used they be-

242

CONCRETE CONSTRUCTION 243

came the most stable part of the structure.
Concrete is practically the only material now
used for the foundations and walls of com-
mercial greenhouses, and to a g^reat extent
it has displaced masonry for private
greenhouses.

At present cement is almost universally
handled and shipped in cloth or paper sacks
holding 95 pounds. It is often spoken of,
and is sometimes quoted by the barrel, 'this
now meaning simply four sacks, or 380
pounds. As a rule, the most satisfactory
form in which to buy cement is in cloth sacks.
The sacks may be returned when empty, and
if not torn a credit of about 10 cents each
may, be realized.

Sand. — Sand, to give the most satisfac-
tory results, should be free from clay or or-
ganic matter, and rather coarse. \^ery fine
sand will require a greater proportion of
cement and aa a consequence the concrete
will be more expensive. In a small way,
sand that contains some organic material
may be washed and thus made satisfactory-,
but it is an expensive process.

24.4: GREENHOUSES

Stone. — Either crushed stone or gravel
may be used in making concrete, the only
difference being that the crushed stone usual-
ly has a cleaner surface and the cement will
cling to it more tightly. When gravel is
used it should be free from clay, and the in-
dividual stones should be clean and bright
and not covered with a layer of clay or soil.

The size of the stones may range from a
fourth to two and a half inches in diameter,
the size depending on the use to which the
concrete is put. The best results are ob-
tained when the sizes vary regularly from
small to large, in order that they may settle
well together when the concrete is poured.

Run of the Bank gravel is sometimes used.
This is economical only when it contains
sand and gravel in the correct proportions,
as explained in a succeeding paragraph.

Crushed Stone may also contain very fine,
medium and coarse stone in the correct pro-
portions, so that no sand need be added, but
such a condition is rare, unless tlie stone is
ground and furnished for this special pur-
pose.

CONCRETE CONSTRUCTION

245

Proportions of Materials. — Theoretically,
the ideal concrete is a mixture in which all
the spaces between the stones or gravel are

C£M£NT

«?7-d?/r2r

COA/C/?£T£

Fig. 127. — Proportions of cement, sand and stone re-
quired to form concrete

filled with sand, and all the spaces between
the grains of sand are filled with cement.
From this it will be seen that the total bulk
of concrete would not be greatly in excess
of the bulk of stone or gravel, as the sand and
cement would go to fill the vacant spaces
(voids). This is really true except that, as
usually proportioned, a slight excess of ce-
ment is allowed. This is wise in order to
insure that there shall be a film of cement
about each stone and grain of sand, so they
may be all bound together in a solid mass.
The common formula for most concrete
work is known as the i :2 14 mixture. In this
there are: i part by measure of cement, 2
parts of sand, and 4 parts of stone or gravel.

246 GREENHOUSES

This is the formula commonly used for walls
above ground and for bridges and similar
work. For sidewalks, floors, etc., which are
supported on a firm foundation and are not
subjected to heavy strain, a weaker mixture
of T part of cement, 2M parts of sand and 5
parts of stone or gravel, is sometimes used.
For plastering the outside of walls and for
similar purposes a mixture of cement and
sand alone in the proportion of i to i is used,
as it is easily worked and leaves a smooth
surface.

Mixing. — For small jobs concrete is
usually mixed by hand. The essentials are:
(i) A tight platform or mixing board of suf-
ficient size; (2) a convenient measuring box;
(3) suitable shovels; and (4) a supply of
water. Quite commonly the sand and gravel
is measured in the wheelbarrows in which
it is hauled, a little experience, secured by
carefully measuring the amount for a few
times, being all that is necessary to insure
sufficiently accurate measuring. The bar-
row loads are checked up from time to time,
however, to see that they are not over-run-
ning or falling short.

CONCRETE CONSTRUCTION 247

It is convenient to mix in batches requir-
ing even bags of cement. For example, a
two bag batch would mean two bags of ce-
ment, a quantity of sand equal to 4 bags
(3^ cubic feet) and 8 bags (7/4 cubic feet)
of stone or gravel. They are mixed together
thoroughly, shoveling over several times be-
fore adding the water.

Amount of Water. — The quantity of water
used has but little effect on the resulting con-
crete, the amount depending rather on the
consistency at which the concrete can best
be handled for the special purpose for which
it is to be used. The dryer the mixture the
more quickly it will set.

For thin walls, or where the form con-
tains many indentations, the mixture should
be thin enough to run off the shovel cfuickly
in handling.

For, walls of medium thickness (6 to 12
inches) or for floors, walks, etc., it should be
jelly-like in consistency, so that it will ])ile
up somewhat on the shovel, but will slowly
settle and run off the sides.

For foundations, underground, where it is
important that the mixture set as quickly as

248 GREENHOUSES

possible, it may be mixed so dry that it will
handle like damp earth. Care must be taken
in making this "dry mixture" that every part
is moistened.

Estimating Materials. — The quantity of
cement, sand and gravel necessary for a giv-
en piece of work may be found by multiply-
ing the number of cubic feet by the percent-
age of cement, sand and gravel in a cubic
foot of the mixture to be used. For con-
venience these proportions are given in tabu-
lar form in terms of barrels of cement and
cubic yards of sand and gravel.

TABLE SHOWING PROPORTIONATE QUANTI-
TIES OF CEMENT, SAND AND GRAVEL IN
A CUBIC FOOT OF CONCRETE

Cement Sand Stone or gravel

Mixture barrel cubic yard cubic yard

1:2 :4 0.058 0.0163 0.0326

1:2>4:5 0.048 0.0176 0.0352

To use, multiply the number of cubic feet
of concrete required by the factor shown in
the table. The result will be the quantity of
the material required.

For example, looo cubic feet of 1 12:4 con-
crete would require

CONCRETE CONSTRUCTION 249

1000 X 0.058 or 58 barrels of cement
1000 X 0.163 or 16.3 cubic yards sand
1000 X 0.0326 or 32.6 cubic yards gravel
In estimating for cement mortar, figure i
cubic foot to each 15 square feet of surface to
be covered. Each cubic foot of i :i sand and
cement mortar requires 0.1856 barrels of ce-
ment and 0.0263 cubic yards of sand.

Forms. — As concrete is soft when mixed,
it is necessary to have some kind of a form
or mold to hold it in the desired form and
position until it hardens. For foundations,
for such structures as greenhouses, a trench
is usually dug 12 or 14 inches wide, and deep
enough so that the bottom will be below
the frost line. If the soil is firm enough to
hold its place no form will be needed, but
the concrete may be poured directly into the
excavation, tamped and allowed to harden.

For that part of the wall which is above
ground, however, a form is needed. It is
important that this form be vertical, that
it be straight, and that it be smooth in tlie
inside so that the resulting wall will be agree-
able to the eye. The making of the forms is
important. They should be built by an ex-
perienced carpenter.

250

GREENHOUSES

Any kind of lumber which is free from
knot holes and has been surfaced to an even
thickness will answer for forms. If the wall
is a high one it may be necessary to tie the
sides of the form together with wire. The
wires remain in the concrete when the form
is removed, but may be cut off flush with the
surface, and if the wall is plastered they will
not be noticed.

Fig. 128. — Form for a concrete wall

CONCRETE CONSTRUCTION

251

Filling the Forms. — In filling the form the
concrete is placed in layers about 6 inches
deep and tamped lightly until water shows

on the surface. This will
insure its settling together
closely- If the wall is not
to be plastered and a smooth
surface is required, a spade
or paddle is run down all
along between the concrete
and the sides of the form
when the concrete is poured.
This will force the larger
stones toward the center of
the wall and allow the
smaller stones and sand to
fill in next to the form, thus

I'l

k-mm

■:^]:Ma

Fig. 129.— Meth-
od of facing a
concrete twall

making a smooth surface.

Reinforcing. — Concrete
will withstand enormous
crushing loads, but in walls where there
is a considerable side strain, it should be
reinforced with iron or steel. The best
materials for this purpose are iron or steel
rods. If they are twisted or roughened in
some manner, so that the concrete will ad-
here to them tightly, their efficiency will be
greatly increased. They are put in the

253 GREENHOUSES

forms, usually vertically, about midway be-
tween the sides and 2 or 3 feet apart before
the concrete is poured.

When an extra strong wall is required rods
may be laid horizontally on the top of every
layer or every second layer as the concrete is
placed and tamped down into the soft mix-
ture. When the walls extend only 3 or 4 feet
above the surface and are at least 8 inches
thick as is commonly the case in greenhouses,
little if any reinforcement is needed.

Walks and Floors. — Concrete walks are
now very commonly used in commercial as
well as private greenhouses, and the boiler
and service rooms are usually floored with
concrete. As the walks are not usually sub-
ject to as hard usage as those laid out-of-
doors, or to the action of frosts, it is not
necessary to make them quite as thick, but in
other respects they differ but little from the
concrete sidewalks now so common.

The common method of building walks in
a greenhouse is to make an excavation a few
inches deep and as wide as the walk is to be
and fill it with broken stone, pieces of brick,
etc., to make a foundation. On top of this,
two pieces of straight 2 x 4-inch lumber are
placed on edge, level with each other and

CONCRETE CONSTRUCTION 253

with their inside edges spaced just as far
apart as the walk is to be wide. They are
then fastened by driving stakes on the out-
side and naihng. The concrete is then
poured into this form to within about an inch
of the top and tamped firmly. A top coat,
usually of finer material, is then placed on
top of the first layer before it is set, and
struck off by running a straight edge along

C-

Fig. 130. — Structure of a concrete walk, a, foundation;
lb, coarse concrete; c, finish coat of fine concrete

the tops of the side pieces. This is then
troweled by hand to give a smooth and
slightly curving surface.

To allow for expansion and contraction,
the walk should be cut into blocks before it
sets. This may be done by putting in pieces
of thin sheet-iron at regular intervals to be
removed when the concrete has partially
hardened. Sometimes the walk is cut
through with a spade while still soft, at regu-
lar intervals and fine, dry sand placed be-
tween the blocks so made. Tliis is usually
quite satisfactory and by careful troweling

254 GREENHOUSES

a very neat walk may be made in this way.

For the lower layer, when there is a firm
foundation, a i :2>^ 15 mixture will be satis-
factory. The top layer should be of a 1:2 4
mixture or, when an especially smooth sur-
face is required, of a 1:2 mixture, that is,
one part of cement and two parts of sand.

Floors are laid -practically the same as
walks, except that they are usually troweled
level instead of curving. The work is begun
at one side of the floor, and as soon as one
section has been laid and has had time to
set, the side boards are taken up and put
down for the next section. Floors should
seldom or never be laid in a solid mass.

Waterproofing. — Much trouble is often
experienced in underground boiler rooms
from water. The- best protection is to lay
a row of tile completely around the
outside of the foundation, at the bottom, and
connect it with the sewer or drain. If the
bottom of the cellar is springy it may be
necessary to lay the floor in a solid piece and
in two layers. After the first layer has set
and become dry, or nearly so, a thick coating
of hot tar may be applied, allowing it to ex-
tend for a few inches up the side walls.
When this has hardened put on another coat

CONCRETE CONSTRUCTION

25o

of rich concrete, troweling it up the sides
as far as the tar has been placed. When an
absolutely watertight job is required it may
be necessary to coat the entire outside sur-
face of the walls with tar and then bank up
with earth.

Several so-called waterproofing materials
designed to be placed in the concrete when

Fig. 131. — A small power machine for mixing concrete

it is mixed are on the market, but as, a rule
they are not fully satisfactor}^

Concrete Blocks. — Blocks made of con-
crete in special molds or forms are sometimes
employed for walls. They are usually hol-
low and for that reason make a warmer and
somewhat dryer wall than does solid, poured

256 GREENHOUSES

concrete. Experience shows that as a rule
they are less durable than solid walls, but
when the cost of material and labor for mak-
ing forms is considered they may be more
economical. They are often made with an
ornamental face resembling broken stone,
and make a somewhat more pleasing appear-
ance than a plain wall.

Cost of Concrete. — So many factors enter
into the cost of concrete that no reliable
general estimate can be given. The price of
cement is now fairly constant and uniform.
The cost of sand and gravel or crushed stone,
on the other hand, differs widely. In some
places it may be had on the premises, in
others it may have to be transported for
several miles. Other factors entering into
the cost are labor and the size of the opera-
tion. Where the quantity of work will justi-
fy the use of a power mixing machine, the
cost is usually less than when the mixing is
done by expensive hand labor, although the
cost for labor may often be greatly reduced
by carefully planning the work.

In general the contract prices for walls on
comparatively small jobs range from 7 to 20
cents per cubic foot, and for walks and floors
from 4 to 15 cents per square foot.

CHAPTER XVI
PLANS AND ESTIMATES

The cost of any kind of a building must
necessarily vary with the cost of building
material and the price of labor. This is es-
pecially true with greenhouses, since the ma-
terials used (glass especially) are subject
to extreme fluctuations in price. In the pre-
ceding chapters it has been the aim to give
all the data necessary for estimating the
amount of material required for any given
house, but no attempt has been made to state
definite prices.

Little can be added in this chapter to what
has already been given, and it would be use-
less repetition to collect the data into one
chapter, as it may be easily found by refer-
ring to the index. An efifort has been made,
however, to make some suggestions as to the
probable cost of difTerent types of houses un-
der varying conditions.

Basis of Estimates. — Since the economic
value of a greenhouse depends on the area of

257

258 GREENHOUSES

surface covered (bench space) it is common
to estimate costs in terms of square feet of
surface covered. In an investigation among
a large number of growers (all types of
houses) the author found that the first cost
averaged not far from 45 cents per square
foot of surface under glass. This included

cost of heating system, but did not include
cost of service buildings.

The cheapest plant on which data was se-
cured was a range of four all wood frame
houses, 16 X 50 feet, which had been in serv-
ice for nine years and which was built at a
cost of $525, or about 22 cents per square
foot. In this case a second-hand boiler was
used. Several larger ranges heated by steam
from a central heating plant have been built
at a cost of between 30 and 40 cents per
square foot, though at a time when material
was low in price. Data on modern semi-
iron construction, when the labor was per-
formed for the most part by the owner and
his help, show a cost of between 50 and 60
cents per square foot, and all iron construc-
tion between 60 and 75 cents per square foot.
All these, of course, were standard commer-
cial houses. Private and public conserva-

PLANS AND ESTIMATES 259

tories and ornamental houses often cost two
and three times as much.

Detailed Estimates. — Detailed estimates
necessarily differ with the grade of material
used. The following is a detailed estimate
at current prices of the material needed for
and the cost of a sem-iron frame house
30 X 90 feet, not including labor of erecting.

850 cubic feet concrete ('wall and piers) —
50 barrels cement
14 cubic yards sand
28 cubic yards gravel $100

PIPE
Side Posts —

32 pieces 2-inch pipe, 5 feet 6 inches
Purlins — •

360 feet V4 inch
Purlin Supports —

24 pieces 1^-inch pipe, 8 feet 3 inches

24 pieces l>4-inch pipe, 11 feet
Cross Ties —

24 pieces 1^-inch pipe, 5 feet

24 pieces T^-inch pipe, 8 feet 6 inches
Pipe and fittings for water lines, 100 feet ^4 inches $75

PIPE FITTINGS

32 Gutter brackets
120 Clamp fittings

48 Foot pieces
140 Purlin clasps $30

MILL WXDRK

240 feet sill

180 feet eave plate

260 GREENHOUSES

90 feet ridge
180 feet drip gutter

4 pieces gable rafter, 18 feet long
268 pieces sash bars, 18 feet long

4 pieces corner bars, 4 feet long
268 pieces glazing bars, 4 feet long
180 feet sash header
330 feet glazing bar
100 feet 2x4 for door casing and gable bracing

1 door
Ventilator sash with stops $200

GLAZING
86 boxes glass (16x24)
500 pounds putty

8000 glazing points $250

Ventilating apparatus $25

Nails and other hardware $25

Paint $50

Freight $15

Miscellaneous items $25

HEATING
Boiler (hot water)
Pipe and fittings
Brick for flue $550

Total $1345

This house covers approximately 2700
square feet of surface, which at a cost of
$1,345 gives a cost per square foot of 49.81
cents for materials, but not including labor.

Figures on a similar house 31 x 100 feet
submitted by a well-known manufacturer of
greenhouse materials are given below:

PLANS AND ESTIMATES 261

WOODWORK

200 feet gutter with drip

100 feet ridge

228 feet glass sill

175 feet gable end bars

4 pieces gable rafters, 18 feet long
144 pieces sash bars, 18 feet long

12 ventilators

12 pieces ventilator sash cap

60 headers
144 side bars

4 corner bars

1 door $177.01

Ventilating machine complete $26.40

Hinges for ventilators 3.60

Trussing material 5.20

Hardware for doors .63

PIPE, POSTS AND FITTINGS (walls)

40 pieces 2-inch, 5 feet long

40 pieces post tops $27.20

Nails 2.50

10 pounds glazing paints 1.30

400 pounds putty 14.00

Paint 32.00

Glass, 4600 square feet 260.00

Purlins, fittings and purlin supports 61.75

Gable bracing material 2.50

Heating plant complete 703.33

Total $1317.42

The latter estimate does not include cost
of materials for walls, but in other ways is
complete. The cost per square foot of sur-
face covered is 43.9 cents not including wall
and cost of erection.

262 GREENHOUSES

For an all wood frame house the cost of
material will probably be from 15 to 25

per cent, less than the above and ♦the cost of

erection from 10 to 20 per cent. less.

For an all metal frame house the cost for

materials will range from 25 to 40 per cent.

greater than for the semi-iron construction,

but the cost of erection will be less.

Information Required for Estimates. — In
writing for estimates the following informa-
tion should be given :

1. Type of house (semi-iron, all metal,
etc.).

2. Kind of roof (even span, three quarter
span, etc.).

3. Length and width (if range, send
sketch showing arrangement).

4. Height to eaves.

5. Pitch of roof or height to ridge.

6. Size of glass preferred.

7. Kind of heat (hot water, steam, vapor).

8. Temperature to be maintained.

9. Coldest outside temperature expected.

10. Kind of fuel (hard or soft coal).

INDEX

PAGE

All-metal frame greenhouses

Asbestos covering for furnaces and pipes . . 218

Beds (greenhouse) ...... 143

curbs for

156

of hollow building tile

145

Benches ....

143

arrangement of

153

concrete

149

for sub-irrigation

241

height and width of

152

iron frame

148

wood ....

146

Boilers ....

20O

accessories for

215

arrangement for steam heati

197

cast iron

205

essentials of .

201

hot water

210

for hard and soft coal .

211

ratings of ... .

212

self stoking

221

steam ....

210

styles of cast iron

208

styles of wrought iron .

209

types of .

203

under-fed

221

wrought iron

205

Cast iron boilers .....•• 208

Chimneys and flues ...... 223

size and height of . . . • • • 225

Coal

cost of 221

heating value of . . • • • • ???

kinds of .

iJiy

263

264

INDEX

Coils (heating)

arrangement of

length of for hot water heati

length of for steam heating
Coldframes

described

construction of
Cold-pits

Concentric system of framing
Concrete construction

blocks

cost of

estimating material

filling forms

forms for

mixing

water needed for

water proofing
Conservatories
Curbs

Curved eave construction
Curved roof greenhouse
Cypress (pecky)

Double glass sash
Drip gutter .

PAGE

164
191
179
190
24
3
24
3,26
78
242
255
256
248
251
249
246
247
254
3
156
60
59

15
1Z

Eave plate

Even span greenhouse

Expansion tank

(id

51
181, 187

Fire surface of boilers .
Flow pipe, how to find size of
Flues

size and height of
Forcing boxes
Forcing houses
Foundations
Framework

classes of

erecting
Framing
Fuels

202
175
223
225

29
3,6

80
79,92
78, 85. 89
218

Gable raftet

INDEX

265

PAGE

Gable roof sash-bed ....

Gearing, ventilator ....

131

Glass

grades of . . . . , .

quantity in box ....

sizes of ..... .

100

substitutes for ....

113

Glazing ......

butted method ....

102

lapped method ....

101

window and greenhouse .

105

Glazing bars ......

Glazing points .....

109

Glazing ladders .....

120

Glazing sill ......

Grate surface .....

201

Greenhouses

architecture of ... .

arrangement of ... .

circular ......

curved eave .....

curved roof .....

erection of .... .

even span .....

evolution of .

5-9

framing ......

78, 85, 89

glass for .....

heating ......

158

lean-to ......

location of .

plans and estimates for .

259

ridge-and-furrow ....

side hill ......

size of ...... •

structural material for . . . .

ventilation of .

121

uneven span ......

Gutter ........

Hanging rail, sash . . . . .

Heat, loss by reflection . . . .

Heating, greenhouse . . . . .

158

by hot water ......

167

by steam ......

188

coils .......

164, 179, 191

combination systems . . . .

163

266

INDEX

principles of .

hot water vs. steam

with cast iron pipes

with flues
High pressure steam heating
Hotbed

construction of

described

heating by flues

location for

manure for

permanent, plans for

sash for .

temporary, plans for
Hot twater heating

advantages of

arrangement of pipes for

estimating radiation for

general principles of

pipe for . . . .

pressure systems

PAGE

158
159
164
159
196

159

169, 178

171,176

167

173

183

Irrigation
overhead
sub-irrigation

Light

loss by absorption

loss by reflection
Location

for greenhouses

for liotbeds

Mats, sash-bed
Manure for hotbeds

240
240
241

97
44

35
11

31
21

Paint

estimating
for iron work
for . shading
kinds of .

Painting

"Pecky" cypress

117
116
118
116
114
77

INDEX

267

PAGE

Pipe

covering- for .......

218

frame . . . . . . .

64,88

paint for .......

116

steel ........

wrought iron .

Pit for hotbed ......

Pitch of roof .......

42, 45-46

Plans and estimates .....

256

basis of .......

257

detailed estimates for greenhouses

259

information required for

262

Plant forcers ......

Pressure systems of hot water heating .

183

Propagating house ......

Pumps

capacity of ..... .

229

for circulating hot water

180

kinds of .

227

power required for .....

229

steam . . . . .

198

Purlins .......

Putty .

104

estimating ......

107

liquid .......

112

Putty bulb

108

Radiation, how to estimate ....

171

Rafters

Rams, hydraulic . . .

232

capacity of ..... .

233

double acting ......

236

plan for installing .....

233

Range of glass, a .

Ridge ........

Ridge-and-furrow houses ....

Roof, pitch of ..... .

Sash ........

cost of ...... .

glazing of ..... .

kinds of .

temporary ......

Sash-bars .......

spacing of ...... .

368

INDEX

Uneven span greenhouses

PAGE

Sash-beds

attached to dwelling ....

classes of ......

gable roof ......

materials, care of .

Sash sill .......

Semi-iron frame houses ....

Shading , h ...... .

118

Shaft hangers ......

130

Shafting, ventilator

128

Shed roof greenhouse . . . . .

Shutters .......

Side hill greenhouse .....

Side ventilating machinery ....

126, 134

Sliding shaft ventilating machine

140

Steam heating ......

188

advantages of .....

160

arrangement of boilers for

197

arrangement of coils for

191

coils for ......

190

general principles ......

188

high pressure ......

196

vacuum and vapor systems

196

Steam pumps and traps ....

198

Stove house ........

Structural material .....

Substitutes for glass . . . . . .

113

. T

Tanks

capacity of . . ...

238

expansion .......

181, 187

height of . . . . .

237

types of ....... .

236

Traps, steam return ......

198

Truss framework ......

Vacuum systems

heating

. ,

196

Vapor systems of

eating

196

Ventilation

o •

. 121-141

overhead

, .

124

side

. .

, ,

123

systems of

, .

124

under-bench

. ,

125

INDEX

2G9

PAGE

Ventilators

arms for

. 136,138

header ....

... 1^

methods of hanging

126

size of .

126

Ventilating machinery-

capacity of . . .

139

chain system .

133

closed column

132

gearing ....

T31

open column . . . .

131

rack and pinion

133

shafting . . . . .

128

side ....

. 134,136

sliding shaft . . . .

140

Walks

ashes used for

concrete .

construction of

materials for .

width of .
Walls . . .

Water supply

amount used in greenhouses .

cost of .

hydraulic rams for raising

pumps for ....

storage tanks for
Waterproofing for concrete
Weather strip ....

Wood, kinds used in greenhouse cons
Wood frame greenhouses
Wrought iron boilers
Wrought iron pipe

, ^

156

, ^

252

156

^ ^

155

. 83, 251

226

227

232

227-228

236

254

truction

205

• • «

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