Cool surfaces and shade trees to reduce energy use and improve air quality in urban areas

Urban heat islands, caused by lack of vegetation and darker surfaces, can increase urban temperatures by as much as 2.5°C, which in turn increases demand for energy for cooling and worsens air quality. Increasing vegetation in urban areas and reducing the albedo of urban surfaces can minimize the urban heat island effect. This paper provides an overview of the existing research regarding tools available for analysis and the direct and indirect effects of “cool” roofs, cool pavements, and trees on energy use and on smog production. Co-benefits, potential problems, and costs of roofs and trees are discussed in detail. Throughout the paper, applications to Los Angeles and the United States are presented.