An Albedo or solar reflectance, is a measure of a material's ability to reflect sunlight (including the visible, infrared, and ultraviolet wavelengths) on a scale of 0 to 1. An albedo

value of 0.0 indicates that the surface absorbs all solar radiation, and a 1.0 albedo value represents total reflectivity. EPA ENERGY STAR specifies an albedo of 0.65 or higher for low-slope roof applications and 0.25 for sloped roofs.

Other definition:
An Albedo is the fraction of the total solar radiation incident on a body that is reflected by it. Albedo can be expressed as either a percentage or a fraction of 1. Snow covered areas have a high Albedo (up to about 0.9 or 90\%) due to their white color, while vegetation has a low Albedo (generally about 0.1 or 10%) due to the dark color and light absorbed for photosynthesis. Clouds have an intermediate Albedo and are the most important contributor to the Earth's Albedo. The Earth's aggregate Albedo is approximately 0.3. See radiation, radiative forcing, photosynthesis.