The most effective measure of a roofing material’s ability to reject solar heat is the solar reflectance index (SRI), a measure of the constructed surface’s ability to stay cool in the sun by reflecting solar radiation and emitting thermal radiation.
However, solar reflectance, or SR, is a better way to measure materials that have more thermal mass, including nonroof materials. SR is the fraction of solar energy that is reflected by a surface on a scale of 0 to 1. It doesn't factor in emissions of thermal radiation the way SRI does.
Question:
What's the difference between SR and SRI?
