The Sustainable Sites Credit, Heat Island Reduction takes into account both new and three-year aged...

SRI generally decreases with age

The Solar Reflectance Index (SRI) is a measure of the ability of a surface to reflect solar heat, as shown by a small temperature rise. It is calculated using the values of solar reflectance and thermal emittance of the surface. The higher the SRI, the lower the heat island effect. However, SRI generally decreases with age due to factors such as weathering, dirt accumulation, and biological growth. Therefore, the Sustainable Sites Credit, Heat Island Reduction takes into account both new and three-year aged SRI values for roofing material to ensure that the material maintains a high level of reflectance over time.