When looking at cities on Google earth, we see a lot of dark surfaces. Most roofing is a dark color. Pavement is typically a dark color. It appears that even the majority of our cars are dark. This all contributes to something called “heat island impact.” To combat this a designer can use light colored materials for pavement, roofing, and reduce paved areas on a site.
The solar reflectance index (SRI) is a measure of the constructed surface’s ability to stay cool in the sun by reflecting solar radiation and emitting thermal radiation. A standard black surface has a SRI of 0 and a standard white surface has a SRI of 100. In order to calculate the SRI of a material you use the solar reflectance and thermal emittance from the cool roof rating council standard. 
You can offset “heat island impact” by using white roofing, white concrete for paving, and vegetative roofs.
