Solar Reflectance and Heat Absorption
Heat lsland Mitigation with Roofs
On a hot, sunny, summer day, traditional roofing materials may reach summertime peak temperatures of up to 190"F (88"C). By comparison, cool roofs only reach peak temperatures of 120"F (49"C).
The term "cool roof" is used to describe roofing material that has high solar reflectance , or albedo. These materials reflect a large portion of the sun's energy. Cool roofs also may have a high thermaI emittance, and thus release a large percentage of absorbed heat. This keeps the material cooler and helps to reduce the heat island effect.
There are two types of cool roofs: those used on low-slope or flat buildings (primarily commercial) and those used on steep-sloped buildings (primarily residential). Most cool roof applications for low-slope buildings have a smooth, bright white surface to reflect solar radiation, reduce heat transfer to the interior, and reduce summertime air conditioning demand. Most cool roof applications for steep-slope buildings come in various colors and can use special pigments to reflect the sun's energy.