28 COMMISSION ON BUILDING DISTRICTS 



walls. To the extent to which this occurs the danger of infection 

 from certain disease germs is lessened. Sunlight has both a physio- 

 logical and psychological influence on human beings. 



" By daylight is meant the indirect lighting from the sun, that is, 

 lighting received from the sky or clouds and reflected from various 

 surfaces. While it is possible for human beings to exist without 

 direct sunlight and even without daylight, it is the experience of the 

 race that both sunlight and daylight in sufficient amounts are highly 

 desirable. Daylight is necessary not only for health and comfort but 

 for economic reasons. Too little light causes eye-strain with its train 

 of physiological disturbances and decreases the productiveness of 

 work. It unfavorably influences the mental condition. Light pro- 

 motes cheerfulness, while gloomy rooms depress vitality. Lack of 

 daylight limits the length of the working day in some industries and 

 increases the amount of artificial light required. Artificial lighting 

 with oil or gas tends to vitiate the air by increasing the carbonic acid 

 and moisture, and even by increasing the poisonous carbonic oxide. 

 Artificial lighting also increases fire risks. Lack of exterior light- 

 ing increases the amount of window space required and this in 

 turn increases the heat loss in buildings in winter. In these and other, 

 ways insufficient lighting not only results in inconvenience to human 

 beings but may be a positive menace to the health, safety and morals 

 of the people. The amount of daylight received in buildings is greatly 

 affected by adjoining buildings, by their positions, their height, and 

 by the character of their walls, both in color and material. 



" The necessity of adequate ventilation need not be argued but 

 it is not as fully realized as it should be that the air which enters a 

 building, both in amount and quality, is influenced by the surrounding 

 buildings. If buildings are too close together there is likely to be a 

 stagnation of the air between them. The ventilation of streets, alleys, 

 courts and interior spaces between buildings is as much a matter of 

 public importance. Street ventilation is influenced not only by the 

 orientation of the streets and the prevailing wind movements, but 

 by the height, size, shape and character of buildings, and their dis- 

 tance apart. In cavernous streets there are excessive air current s 

 near the ground, and at times great air movements, especially ob- 

 jectionable in winter. On the other hand, at times of gentle air move- 

 ments there may be no currents at all near the streets and pavements 

 between high buildings because the friction of the air passing through 

 the narrow channels prevents them. In other words, narrow street s 

 lined with high buildings tend to produce extreme conditions of air 

 movement and both extremes are objectionable. In regulating the size 

 and height of buildings with reference to the streets the city is to a 

 considerable extent controlling street ventilation and the ventilation 

 of courts and interior spaces, and thus indirectly, the ventilation 

 of indoor quarters. 



