16 VEGETABLE FORCING 



houses covering the same area ; furthermore, there is not 

 so much air to be re-heated. The large house, therefore, 

 requires less radiating surface and less fuel. 



The length of the house is not of great consequence, 

 although unusual length should be avoided. Most of the 

 largest houses vary from 200 to 600 feet in length. Two 

 hundred feet is probably the maximum which can be 

 heated satisfactorily with the gravity system of hot 

 water, but with forced circulation the largest ranges may 

 be heated economically with hot water. 



Tig. 3. Two-acre, three-quarter-span hillside house near New Castle, Pa. 



Commercial houses are built much higher than for- 

 merly. For many years it was the belief that to obtain 

 the best results the glass must be near the plants. Suc- 

 cessful growers, however, have learned that better crops 

 may be grown in higher houses. The distance from 

 ground to gutter varies from 5 to 9 feet in the large 

 modern houses, 6^ feet probably being the most popular 

 height. There must be ample room for the training of 

 plants and, in connected ranges, for workmen to walk 

 from house to house without striking their heads on th~ 

 gutters. High houses make it possible to provide free 

 ventilation without, subjecting the plants to cold drafts 



