November, 1910 



AMERICAN HOMES AND GARDENS 



451 



determine its cubic contents and also its glass surface area. 

 The problem of house heating is much simpler than for 

 a conservatory or greenhouse, for in the first there is no 

 glass roof to consider. The method of finding out how 

 much heat is required for a greenhouse is to multiply the 

 length by the breadth of the house to determine the num- 

 ber of square feet on the ground. When this measurement 

 is obtained add to it one-third to make allowances for the 

 pitch of the roof and the glass ends. The figure thus ob- 

 tained will give approximately the number of square feet 

 of glass exposure. Some houses have a belt of side glass 

 around one side and the ends. In such instances the num- 

 ber of square feet of this side glass should be obtained 

 and added to the above. Most houses do not have the 

 side glass, and the first rule covers their case entirely. 



As an example of this method of computation, suppose 

 the greenhouse is 20 by 80 feet in ground measurement. 

 The computation of the glass area would be as follows: 



20 times 80 equals 1600, divided by 3 equals 533. 



1600 plus 533 equals 2133 square feet of glass. 



If there is a two-foot belt of glass around the long side 

 we would have to add to the above 2 times 80, or 160 

 square feet, making a total of 2293 square feet of glass sur- 

 face. Heat losses are much greater in greenhouses than 

 in other buildings, and it has been necessary to construct a 

 table of heating averages rather higher than for residences. 

 The tables of heating averages below are used successfully, 

 and they answer all purposes in determining the amount of 

 heat required for any conservatory or greenhouse. From 

 these tables, and the measurements of the house, it is then 

 a simple matter to determine the whole question of heat 

 ing. As most greenhouses are heated to-day by either 

 steam or hot water, tables have been prepared for these 

 two methods of heating only. 



STEAM HEATING. 



Sq. ft. glass Coil or radiating 



Temperatures surface surface 



o to 50 degrees yj^ i sq. ft. 



o to 60 degrees 6 . i sq. ft. 



o to 70 degrees 4^/^ i sq. ft. 



o to 80 degrees 3 i sq. ft. 



HOT WATER SYSTEM. 



Sq. ft. glass Coil or radiating 



Temperatures surface surface 



o to 50 degrees ^H i sQ- ^t. 



o to 60 degrees 3 i sq. ft. 



o to 70 degrees 2}i i sq. ft. 



o to 80 degrees i^ i sq. ft. 



Now to obtain the temperature desired in a greenhouse 

 of the size mentioned we must divide the total amount of 

 glass surface by the figure in the middle column. For in- 

 stance, if we want a temperature of 60 degrees with a hot 

 water system we divide the total glass surface of 2293 by 

 3, which gives us 765, which is the number of square feet 

 of radiating surface required to produce this temperature. 

 Or if a steam plant is installed, and a temperature of 60 

 degrees is desired, we divide the glass surface by 6 and 

 obtain our radiating surface. It is a very simple matter 

 thus to work out the problem of radiating surface needed 

 for any temperature. Much, of course, depends upon the 

 heating plant, and to make the rule accurate it should be 

 understood that these results are obtained in a plant where 



the temperature of the hot water carried is 180 degrees at 

 the heater. If a steam plant is used the estimates are based 

 on a temperature of 219.5 degrees Fahrenheit or a pressure 

 of 2 pounds. With a plant that can maintain these tempera- 

 tures the above working rules will prove all right. 



The largest item of cost in raising flowers or vegetables 

 under glass is the fuel. The cost of heating is therefore 

 of the first consideration, and anything which will cut down 

 the cost of fuel will prove of great benefit. Under modern 

 methods of heating with steam and hot water greenhouse 

 culture of plants has advanced wonderfully, and it is pos- 

 sible to raise many kinds of fruits and flowers in the middle 

 of winter that could not be attempted under the old systems 

 of hot air. The tendency to-day is. to increase the height 

 of the greenhouses, and this of course involves a greater 

 expenditure for fuel. 



The heat losses in either conservatory or greenhouse are 

 considerable, especially through the laps of the glass roof 

 and around the ventilators. There is, of course, a great 

 amount of condensation on the surface of the glass form- 

 ing the roof and walls, and this has an important action 

 upon the general temperature. The method of heating 

 greenhouses to-day is accomplished by circulating or turning 

 the air within the room or structure. It is the turning 

 circulation of the warm air which causes great condensation 

 on the glass. In the early greenhouses the hot air flue 

 method of heating was depended upon, and as a result one 

 end of the place would often be so hot that plants were 

 wilted while at the other end they were chilled with the 

 cold air and their growth stunted. In addition to this they 

 were often damaged by escaping gases. The abandonment 

 of this type of heater and the adoption of hot water and 

 steam heating immediately helped the commercial green- 

 houses. 



The use of greenhouses and conservatories for private 

 residences is steadily increasing, and even the small country 

 home is often provided with conservatories where a few 

 plants can be raised through the winter. The conservatory 

 attached to the side of the house, usually on the sheltered 

 sunny side, offers different heating problems to the detached 

 conservatory or big greenhouse. The principal question 

 involved in such a home conservatory is to design and con- 

 struct it so that the heating can be connected with the heat- 

 ing plant of the living-house. This can be accomplished 

 under certain conditions, and not under others. In the first 

 place the conservatoTy +0- take its hrat ^om the main resi- 

 dence plant must have a southerly exposure and be pro- 

 tected by the house on at least one or two sides. Further- 

 more it must not be too large, and the steam or hot water 

 plant of the house must be large enough to carry an excess 

 of heat units for ordinary emergencies. The extra piping 

 and radiators installed for the conservatory might over-tax 

 the heating plant so that neither the house nor the conserva- 

 tory could be properly warmed. If the furnace is large 

 enough to heat the house to 80 degrees in zero weather 

 there is surplus heat enough to supply the few extra square 

 feet of radiating surface in the conservatory. Before build- 

 ing an additional conservatory to the house it is well to 

 consider the heating problem carefully, for this will be the 

 most vital question in the long run. If a separate heating 

 plant will be required the cost will amount to considerable, 

 and if the heat drawn from the house is going to cool off the 

 living-rooms in cold weather it is a doubtful expediency. 



