GENERAL CONSIDERATIONS 45 



of the sun be conserved during the short days 

 of winter. At its lowest period the sun rises, 

 in the latitude of New York, scarcely more 

 than 25 degrees above the horizon at noon. 

 In order for the roof to present an angle of 

 90 degrees to the sun's rays at this season, 

 it would need to have a pitch of 65 degrees. 



Fig. 26a. Diagram showing pitch of roof necessary to 

 present an angle of 90 degrees to the sun's rays in winter 



Such a roof would be (i) very expensive to 

 build and maintain, (2) would present too 

 large an amount of radiating surface for the 

 space covered and (3) would be too high to 

 be practical in houses more than 10 or 15 

 feet wide. 



If, however, we reduce the pitch to 35 de- 

 grees, the sun's rays will strike the roof at 

 an angle of about 55 degrees which, by refer- 

 ence to the table, will be seen to incur a loss 



