ROOF REFLECTANCE
Changing roof reflectance will reduce the energy use of a building and affect the size of heating or cooling equipment needed. A change in energy use or a change in equipment size or operational time can lead to energy cost savings.
It is common experience that sunlit objects become hotter than others. This is true for roofs. It is possible that one could comfortably touch one roof yet find the touch of another uncomfortable under the same climatic conditions. Just how hot a roof gets depends on the roof surface solar reflectance.
Highly reflective surfaces are often thought of as being “white.” Dark-colored roofs, which generally have low reflectances, are typically much hotter than white roofs during daytime hours and can easily reach temperatures of 165F during clear, sunny conditions.
The prevalence of asphaltic materials in built-up roofs means that many existing low-sloped roofs are dark in color and have a low solar reflectance. The most notable examples of reduced energy costs come from replacing traditional roofs with white roofs on buildings with high air conditioning loads. The prospects of reduced energy costs, along with the lower surface temperatures of white surface, have been instrumental in creating a strong demand for high reflectance, elastomeric roof coatings.
