Even with the mounds of literature and white papers on technical studies, building owners and managers still have misconceptions and gray areas about cool-roof applications.
Myth #1: Eventually, all white roofs turn gray and all black roofs turn gray, so there is no long-term benefit from installing a cool roof.
Typically, the reflectivity of a light-colored roof will decrease about 20 percent during its first year according to an LBNL study. Another study found that solar reflectance of white-coated roofs can drop 25 percent, with most of the loss occurring in the first and second year.
The solar reflectance of cool roofs tends to decrease over time, but another study by LBNL showed that washing a weathered cool-roof membrane resulted in a significant solar reflectance increase. Other studies have shown that modest cleaning can restore 90+ percent of the original solar reflectance.
Some cool roof membranes also have a higher resistance to dirt accumulation than others, so budget-conscious organizations might have to weigh the resulting increase in energy use for a dirty membrane against the cost of cleaning. For a detailed analysis and case study by RAMCON on cool reflective roofs and how keeping your roof clean pays off, visit http://bit.ly/oZcQMr
Myth 2: Using a cool-roof product when reroofing minimizes the need for insulation.
While it is true that using a cool roof on a building with a low level of insulation can generate greater energy savings, an energy–efficient roofing system should have adequate insulation in addition to a solar-reflective surface. To find out what is the optimal amount of insulation for a given location, you can refer to the International Energy Conservation Code. You can find it here: http://bit.ly/oAAy4Q
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