GREENHOUSE HEATING 



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(A) Table showing relation of glass surface, radiating surface, and heating 



surface ^ 



For instance, to maintain the temperature of a greenhouse 70° 

 at zero weather, there should be 1 square foot of radiating sur- 

 face for 4.0 square feet of glass for hot-water heating, in which the 

 maximum temperature of the water is maintained at 180°; or 

 there should be 1 square foot of radiating surface for 5 square feet of 

 glass for low-pressure (under 5 pounds) steam. These numbers are 

 given somewhat greater by some authorities, and there is no doubt 

 that if the house is not much exposed, higher proportions will give 

 satisfactory results. 



The preceding table gives more exact values for these quantities, 

 and will be found to accord with the best practice in heating of green- 

 houses, either by steam or hot water. Each pound of coal burned on the 

 grate will transfer to the water or steam in the heater about 9000 

 B.T.U As the amount of coal consumed can be varied with the 

 draft or firing conditions, it is evident that no fixed rule can be given 

 for the proportion of grate to radiation. 



1 From Carpenter's work on "Heating and Ventilating Buildings." 



2 British Thermal Unit, — heat required to raise 1 lb. of water 1 degree. 



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