The Solar Reflectance Index (SRI) is an objective measurement of how a given surface reacts to heat. This may include the surface temperature of the material, how much heat is reflected away from the material, and how much heat is absorbed.
ASTM E1980 is specifically designed to determine the SRI of low-sloped and horizontal opaque surfaces in standard conditions. This test method is often used to evaluate roof tiles. In this context, the SRI may help quantify how much heat is absorbed into the roof tile, conducted into the structure, or reflected away from the building.