sentences:  The primary metric in opaque components is the Solar Reflectance Index which accounts for both solar reflectance (albedo) and emittance of a surface.Materials with high SRI will reflect and emit a majority of heat energy, keeping them cooler than other exterior finishes.This is quite significant in the design of roofs since dark roofing materials can often be as much as 50 C° hotter than the surrounding air temperature, leading to large thermal stresses as well as heat transfer to interior space.