What is the term for the overall measure of a material's ability to reflect the sun's energy?

The term that describes a material's ability to reflect the sun's energy is albedo. Albedo is defined as the ratio of the light reflected by a surface to the total light incident upon it. It is an important property in roofing materials as higher albedo values indicate better solar reflectance, which can contribute to lower cooling costs and improved energy efficiency in buildings.

In contrast to albedo, emissivity refers to how well a surface emits energy in the form of thermal radiation, which is not directly related to solar reflection. The R-value measures thermal resistance; it indicates how well a material insulates against heat flow rather than its reflective properties. Thermal conductivity quantifies how easily heat can pass through a material, again unrelated to the material’s ability to reflect sunlight. Understanding these distinctions is essential for evaluating materials for roof surfacing and their effectiveness in energy conservation.