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GREENHOUSE CONSTRUCTION AND HEATING 1 
to find single houses covering an acre or more of land, 
and there are a few ranges (Fig. 1) that cover from 4 
to 10 acres of land. 
Houses vary greatly in width. The majority of the 
oldest houses range from 9 to 12 feet wide. The even, 
connected ridge and furrow type, so common in the West, 
varies from 15 to 18 feet wide. Numerous commercial 
houses are from 20 to 24 feet wide. The 27-foot standard 
house of the West has many advocates, and its width is 
considered by some of the experienced growers the 
maximum for best results. 
In New York, New Jersey and Pennsylvania 30 to 34- 
foot houses are common, while Boston inclines toward 
the 40-foot three-quarter span. (Fig. 2.) Much wider 
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Fig. 2.—Typical three-quarter-span houses of the Boston district. 
houses than these have been built and used for vegetable 
forcing. There is, at New Castle, Pa., a hillside three- 
quarter-span house (Fig. 3) that is 120 feet wide; anda 
house of similar form, built on level ground, at North 
Wales, Pa., that measures 172 feet in width. These are 
very unusual structures. 
Wide houses should be considered with special refer- 
ence to economy of heating. In actual practice the air in 
a wide house with greater height cannot be changed as 
often in a given period as that in two or more narrow 
