178 



COMMISSION ON BUILDING DISTRICTS 



on the opposite side of the street 28 per cent of the sunshine period on 

 a north and south street is cut off by the thickness of the wall in which 

 the window is set. Where the opposite buildings rise to a height above the 

 window equal to .2 times the width of the street, 35 per cent of the sun- 

 shine period is cut off; where it rises to a height .4 times the width of the 

 street, 44 per cent is cut off; .6 times, 54 per cent; .8 times, 65 per cent; 

 1.0 times, 77 per cent; and 1.35 times, 100 per cent. This is for a wall 

 14 inches thick. For a thicker wall the percentage would in eacli case be 

 more ; for a thinner wall less. 



A window in a north and south street situated in a position where the 

 height of the buildings opposite it is .2 times the width of the street above 

 its center level receives direct sunlight for a period the length of which is 

 only 72 per cent of that received by an unobstructed window ; where the 

 height of the buildings opposite is .4 times, 50 per cent ; .6 times, 33 per 

 cent; .8 times, 21 per cent; and 1.0 times, 12 per cent. 



The duration of the sunshine period on the facade and in the rooms 

 on a north and south street at the winter solstice is shown in the following 

 table for different points below the top of the opposite buildings : 



Sunshine Period on North and South Street at New York, December 21st (40° 

 North Latitude) 











Per Cent of 











Period That 



Height of Op- 





Minutes of 



Per Cent of 



Sunshine En- 



posite Build- 



Minutes of 



Sunshine En- 



Sunshine Pe- 



ters Window 



ings Times 



Sunshine Strik- 



tering Window 



riod of Street 



at Different 



Street Width 



ing Entire 



in Wall Four- 



Facade Cut Off 



Heights in 



Above Center 



Street Facade 



teen Inches 



Fronr Window 



Terms of That 



of Window 





Thick 



at Each Height 



Entering Un- 

 obstructed 

 Window 



.0 



275 



198 



28 



100 



.1 



247 



170 



31 



85 



2 



219 



142 



35 



72 



.3 



195 



118 



40 



60 



A 



175 



98 



44 



50 



.5 



156 



79 



49 



40 



.6 



142 



65 



54 



33 



.7 



129 



52 



59 



26 



.8 



118 



41 



65 



21 



.9 



108 



31 



71 



16 



1.0 



100 



23 



77 



12 



1.3S 



77 







100 







Sunshine obtained on the street 



A north and south street at New York improved with buildings on 

 only one side of the street receives at least four hours and 35 minutes of 

 sunshine at the curb level on all parts of its surface on December 21st. If 

 buildings are erected on both sides to a uniform height of one-half times 

 the street width the entire surface of the street at the curb level 

 receives but two hours and 36 minutes sunshine. If the buildings are in- 

 creased in height to one times the street width the pavement receives only 

 one hour and ten minutes sunshine. In case of buildings two times the 

 street width the sunshine period is one hour; two and one-half times, 47 



