CONSTRUCTION OF GREENHOUSES 121 



policy to build a large house or an extensive range of 

 houses without thorough experience in greenhouse work 

 and full knowledge of local conditions and market facili- 

 ties. A house 30 x 100 feet is probably as large as any 

 market gardener should start with, and a smaller struc- 

 ture would be desirable where both capital and experience 

 are limited. A width of 30 feet has been given, because 

 this is the minimum width for economical construc- 

 tion, heating and operation ; narrower houses do not pro- 

 vide as uniform atmospheric conditions, and the plants 

 are more likely to be injured by direct cold drafts. 



174. Location and position. While the natural pro- 

 tection of woods or hills on the north and the west sides 

 is highly desirable, greenhouses should not be con- 

 structed where they will be shaded by other buildings. 



The position of the house with reference to the points 

 of the compass is apparently of little importance. A 

 three-quarter span house should run east and west to get 

 the full benefit of the sun, while the even span house 

 should probably run north and south in order to secure 

 a uniform distribution of light. Some growers compro- 

 mise and build their houses northeast and southwest. 

 With the modern house, about 95 per cent of which is 

 glass, ample light will enter the house whatever its 

 position may be. 



175. Materials used in construction. Serviceability, 

 durability, and economical construction and operation 

 are the main points to keep in mind when building green- 

 houses. No one denies that the full iron form of con- 

 struction is the most durable and that it is also highly 

 satisfactory when in operation, but the cost of construc- 

 tion is beyond the means of most vegetable growers. 

 Again, it is doubtful whether full iron construction is the 

 most economical in the end ; the first cost is from one- 

 third to one-half greater than for semi-iron construction, 

 and this additional expense may exceed the cost of re- 



