The Solar Reflectance Index (SRI) is a numerical expression of a constructed surface’s ability to reflect solar heat. SRI values are derived from a calculation in ASTM E1980 which uses a roof’s solar reflectance, thermal emittance and medium wind coefficient to generate a unit-less value from 0 to 100. A standard black (reflectance 0.05, emittance 0.90) is 0 and a standard white (reflectance 0.80, emittance 0.90) is 100.
The higher SRI values indicate a roof whose surface temperature is lower, thereby reducing heat gain in the living space beneath the roof. Green building rating tools such as Leadership in Energy and Environment Design (LEED) and Malaysia’s Green Building Index (GBI) encourage using building materials with high SRI values to reduce the intensity and impact of the Urban Heat Island (UHI) effect.
SRI Values required by LEED & GBI
Roof Slope SRI
Low-Slope _ 2/12 78 or greater
Steep-Slope > 2/12 29 or greater