Within the LEED rating system heat islands are defined as “thermal gradient differences between developed and undeveloped areas.” Put simply, urban areas retain heat much more than rural areas. Concrete can provide reflective surfaces that reduce the heat island effect to provide a more comfortable living environment and decrease energy consumption.
The temperature of a surface is dependent on the reflectance and emittance of the surface and the influence of solar radiation. To determine these qualities the USGBC employs the Solar Reflectance Index (SRI), which is a composite index calculated in accordance with ASTM E 1980. Baseline SRI values range from 100 for a standard white surface to 0 for a black surface. Ordinary concrete made with Portland cement has an SRI ranging from 38 to 52 which can then be further increased by specifying light colors or using white cement.