Cool Roofs and Heat Islands
"On warm summer days, a city can be 6 to 8°F warmer than its surrounding areas. This effect is called the urban heat island. Cool roof materials, pavements, and vegetation can reduce the heat island effect, save energy and reduce smog formation. The goal of this research is to develop cool materials to save energy and money." 
The Cool Roof Calculator developed at the Oak Ridge National Laboratory is a useful tool for exploring the benefits of cool materials.