GREENHOUSE ARCHITECTURE 51 



Lean-to houses not only have the advant- 

 age over other types in less first cost, but 

 also in cost of maintenance. They have less 

 glass surface in proportion to the area cov- 

 ered; hence there is less breakage, and for 

 the same reason they radiate less heat. For 

 amateur use, especially when they can be 

 erected against the south side of the dwell- 

 ing, they may be built and operated at small 

 cost and will afford much pleasure. 



Even-span or Span-roof Houses. In these 

 houses, as the name indicates, the sides of 

 the roof are of equal length. They are 

 the most popular form, fully 80 per cent, of 

 all houses of recent construction being of 

 this type. They are superior to the lean-to 

 in that they admit light from two sides, and 

 also because they may be run either north 

 and south, or east and west, as may be de- 

 sired. On this point, however, practical 

 growers disagree, some preferring the east 

 and west arrangement, others the north and 

 south. Theoretically, the points in favor of 

 and against each seem to about counterbal- 

 ance. They are stated in the following- 

 paragraph. 



The north and south arrangement permits 



