44 



GREENHOUSES 



Fig-. 26. Diagram showing how heat and light are lost 

 by reflection 



angle, the amount reflected increases as the 

 angle of incidence increases. The amount of 

 the sun's energy lost by reflection when the 

 rays strike the roof at various angles is 

 shown in the following table. 



Table showing per cent, of sun's energy lost when the 

 rays strike the glass at different angles 



Angle of ray Loss by reflection 



60 degrees 2.7 per cent. 



50 

 40 

 30 

 20 

 15 

 10 



3.4 

 5.7 

 11.2 

 22.2 

 30.0 

 41.2 



It is apparent that the maximum amount 

 of the sun's energy may be secured by a roof 

 presenting to its rays an angle of 90 degrees. 

 It is especially important that the energy 



