In his article "Roofing's dirty secret," April issue, page 26, Tom Hutchinson, principal of Hutchinson Design Group Ltd., Barrington, Ill., points out some issues regarding reflective roofs that are important for contractors. We at SPRI believe it is important to provide additional insight and information concerning these issues.
Just as cars and trucks get dirty, contractors also should expect roofs exposed to the same environment will get dirty, too. Car washes became popular years ago when some entrepreneurs learned people valued clean cars for maintenance and technical reasons, such as eliminating corrosive salt. Will the aesthetic and technical value of a clean roof result in a new industry? That question will remain unanswered until the total value equation is developed, understood and implemented.
SPRI takes exception to Hutchinson's claim that "dirty roofs" have been ignored by the industry. Quite the opposite, the soiling of roofs has not been ignored by manufacturers, ENERGY STAR® or the Cool Roof Rating Council (CRRC). In fact, SPRI members began a study of the soiling of roofs in 1998 and published two papers about the subject.
ENERGY STAR allows cleaning of roofs before their three-year aged solar reflectance value is measured based on a belief that rain just before sampling might clean a roof, as well. CRRC decided cleaning a roof after three years of aging should not be done because doing so may inappropriately affect the measured solar reflectance. However, this concept has not been presented aggressively enough to roofing contractors. Manufacturers aim to more proactively help contractors understand the facts.