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. 
Vig. 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, 614 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 the 
gutters. High houses make it possible to provide free 
ventilation without subjecting the plants to co'd drafts 
