By Kristopher Settle
Looking to be a little cooler this summer? Buying an electric fan or an air conditioning unit is effective, but that’s hardly the only way to maintain the temperature in the home, at the office or elsewhere.
Some methods don’t even require any electricity. The concept of a ‘cool roof’ isn’t new, but since over 90% of all roofs in the US are still dark-colored, they’re not widely implemented at this time. The premise is fairly straight-forward; rather than having a rooftop that absorbs the sun’s rays and increases building temperature, painting or tiling a highly-reflective surface on the roof will reflect the rays away from the building, keeping heat away and reducing cooling costs. It is a more complicated procedure than simply painting a roof white, as there is a specialized coating material that emphasizes solar reflectivity and high infrared emissivity. The Sacramento Municipal Utility District (SMUD) estimates cool roofs stay 50-60°F cooler on hot summer days, keeping cooling costs down.
Although there are various colors and materials used for ‘cool roofing,’ the standard is a highly-reflective white paint. The paint creates a higher albedo, or reflection coefficient, which causes sun rays to bounce away from the surface. The albedo coefficient ranges from zero to one, with one being a perfect reflection of a white surface. A corrugated roof has an albedo around .10-.15, a tar and gravel roof is around .03-.2 and colored paint is generally in the .15-.35 range. Highly-reflective paint, however, gives a roof an albedo between .6 and .7.
Some major communities are starting to take notice of the benefits of implementing cool roofs. I’ve already mentioned SMUD, which offers tax incentives per square foot of cool roof installed and also promises an average of 20 percent on future air conditioning costs through their program. New York City also has a cool roofs initiative, resulting in over 3.7 million square feet being ‘cooled.’ The graphic above, courtesy of the NYC website, illustrates the difference between various rooftop materials and their effectiveness in reducing rooftop temperature.
Announced this week, Pittsburgh also started its own cool roof program. Plans include covering 10 city-owned buildings, encompassing approximately 50,000 square feet of rooftop space throughout Pittsburgh. Pittsburgh Mayor Luke Ravenstahl added, “It’s another step in our efforts to make Pittsburgh a more green and sustainable city.”
Authorities have requested volunteer assistance for the project and if you’re in the area and are interested in participating, call 412-255-2280 or email servepgh(at)pittsburghpa(dot)gov for more information.