198 COMMISSION ON BUILDING DISTRICTS 



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 lighting in- 

 creases the amount of window space required and this in turn decreases 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 day- 

 light 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. 



Ventilation 



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 build- 

 ings 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, as the ventilation of 

 rooms is a matter of individual importance. Street ventilation is influenced 

 not only by the orientation of the streets and the prevailing wind move- 

 ments, but by the height, size, shape and character of buildings, and their 

 distances apart. In cavernous streets there are excessive air currents near 

 the ground, and at times great air movements, especially objectionable in 

 winter. On the other hand, at times of gentle air movements 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 streets lined with high buildings tend to 

 produce extreme conditions of air movement and both extremes are objec- 

 tionable. 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 ventila- 

 tion of indoor quarters. 



Quite as important as the volume of the air taken into buildings, is its 

 cleanliness. One of the difficulties in cities is to obtain proper air inlets 

 for ventilation systems. The amount of smoke and dust, foul odors on the 

 streets, bad smells from buildings, from passing vehicles, from exposed 

 refuse and from other sources are matters properly subject to the control 

 of the health department, but the concentration of dust and smoke and foul 

 odors is greatly influenced by street ventilation. The regulation of buildings 

 is a regulation of the amount of dilution of odors, and is, therefore, a public 

 health factor. 



Vegetation 



It is becoming more and more recognized that vegetation is very desir- 

 able in residential districts for reasons of health and comfort. Vegetation 

 cannot thrive without sunlight and it is a matter of history that the increas- 

 ing height of buildings has driven out the trees from streets, while the 

 extension of buildings over large percentages of the lot have left little 

 chance for vegetation of any kind. Trees, shrubs, and grass tend to cool the 

 air during hot weather. Trees produce desirable shade, and yet in winter 

 they do not obstruct the sunlight. Trees therefore furnish a shade which is 

 automatically adjustable, increasing when it is most needed and decreasing 

 when objectionable. In this respect the shade of trees differs from the 

 shade of buildings 



