Solar ReflectanceMore roofing definitions
Solar reflectance measures how strongly an object reflects sunlight. Also called albedo, from the Latin word whiteness, solar reflectance applies only to heat from the sun and not to the reflectivity of light from other sources.
Solar reflectance is measured from 0 to 1. A material rated 0 absorbs all solar heat and light, while something rated 1 reflects all solar radiation. For example, dark surfaces like pavement and black cars absorb a lot of heat so they will have an albedo closer to 0. Lighter materials, such as white clothing and light-colored houses reflect more heat than they absorb and will have an albedo nearer to 1.
Solar reflectance is an important characteristic in roofing as warmer climates will require the use of materials that have high reflectance so that the home will stay cool and and absorb as little heat as possible. The opposite is true in colder climates where dark roofs are more common so that heat from the winter sun's is absorbed to help keep the house warm.
The ENERGY STAR program specifies that low-slope roofs should have an albedo of .65 or higher while an albedo of .25 is required for more steeply-sloped roofs.