There are many reasons building owners clean their roof systems—aesthetic preference, functional use, and to assist in roof system inspection and maintenance. But the idea of cleaning a roof system to allow a roof membrane to perform one of its intended functions—reflecting the sun's rays—generally has been ignored in the roofing industry.
Although the "cool" roofing movement was unknown a few years ago, it is gaining momentum because of the concept that roof surfaces can provide energy savings. There are numerous points of discussion regarding this concept, but one that remains seemingly unaddressed by many manufacturers, code bodies, associations and the research community is that roof systems get dirty. What has been circulated to government agencies, code bodies, and the design and roofing communities is the hypothesis that white roofs will save energy, but the issue of cleaning roof surfaces to maintain reflectivity rarely is brought into discussion. In fact, some manufacturers have gone to the extent of declaring they never promised a roof would stay white.
Following are my thoughts and opinions regarding the means, methods, effects, consequences and realities of cleaning soiled roof surfaces to maintain roof reflectivity.
Ignoring the issue