Passive systems to improve air quality and reduce heat retention in the urban environment

Passive systems are explored as a means to abate two major environmental problems plaguing metropolitan areas - poor air quality and heat retention. As the sources of these problems are diffuse, the solutions must also be diffuse and dispatched throughout the urban framework. A passive system is one that can be incorporated into an existing infrastructure and can function only utilizing primary energy sources. Two types of passive systems are discussed in this chapter - photocatalytic building materials, which utilize sunlight to drive the chemical conversion of air pollutants, and vegetative cover, which is a sink for air pollutants and a source of passive cooling.