Few home builders or homeowners opt for energy-efficient cool roofs, says California building science consultant Steve Easley, because that traditionally has meant the roof has to be white. But that’s changing.
Now manufacturers—with the help of research conducted by the military—have devised a formula for treating shingle-topping granules so darker colors—as deep as forest green, brown, and even “cool” black—also reflect enough heat to make a difference in how hot the home’s attic gets and how high the owner’s cooling bill soars.
Combine the new technology with California’s Title 24 stipulations that require pros to increase the roof’s efficiency, and cool roofs appear to be gaining acceptance, especially among green builders. Add to that the attention of contractors and consumers looking to earn points toward green certification, or who just want to reduce a home’s overall energy costs, and reflective or cool roofing materials—available in asphalt, metal, and composite—could slowly move into the mainstream.
If you or your customers are thinking about a cool roof, which in some cases carries a higher price tag than traditional asphalt shingles or metal, here are six facts to consider:
Heating bills. A reflective roof can help keep a house cooler when the hot sun beats on it, but it will not lower a home’s heating bill, and may even slightly raise it. It makes sense to install a cool roof, which reflects heat but does not absorb it, only where the summers are extremely hot or humid. Most residential cool roofs are in southern and southwestern states, although homes where the summer air is especially humid—in cities like New York, Washington, or Indianapolis, for instance—also are candidates. Still, the Cool Roof Rating Council (CRRC) says cool roof owners may pay slightly more to heat their homes, although the summer savings outpace the increased heating bill.
Performance ratings. The Cool Roof Rating Council uses two measures to rate the performance of cool roofs. The first, solar reflectance, refers to how much of the sun’s energy is reflected by the roof. The other, thermal emittance, measures how well the product releases any heat that it does absorb. Both use a scale from 0 to 1, with those measuring closer to 1 performing best.
Energy Star savings. The council estimates that a cool roof can save a homeowner 7% to 15% in cooling costs. Energy Star recognizes cool roof products that reduce peak cooling demand by 10% to 15%. To obtain the Energy Star label, steep-slope products must have an initial solar reflectance of at least 0.25. Three years after installation, the roofing product must achieve a solar reflectance of 0.15 under normal conditions. Energy Star does not require third-party certification of performance. CCRC, which measures performance but does not impose minimum levels, verifies that the products perform at the levels stated by the manufacturer.
Higher prices. Some pros find cool roofing products garner more interest than sales because of their higher price tag. In the Northeast, for example, Tamko’s Lamarite slate composite cool roof shingles cost $80 more per 100 square feet installed than the non-reflective Lamarite products, estimates Tim Lutrell, a Tamko vice president. “A lot of folks ask about this stuff, but as you go to higher prices, some folks get scared off,” agrees Scott Heitmeier, business manager of steep-slope roofing for ABC Supply. “That’s something that has to be dealt with if these products are truly going to gain their share in the market.”
Long-lasting results. Some studies claim that cool roofs last longer than traditional products because they do not absorb heat. Tucson roofer Daniel Roberts finds that to be true. “Darker shingles naturally will cook at a hotter temperature and tend not to hold up as well as the lighter color,” says the founder and owner of Castle Roofing. “A good rule of thumb in Arizona: The lighter the shingle the better, not just for reflection and energy savings, but for the shingle’s life itself.”
In fact, notes Roberts, he was installing light-colored shingles on Tucson rooftops long before “cool roofing” became an energy-efficiency buzzword. “It’s nothing new.”
Insulation issues. Thick insulation and radiant barriers can cancel out the need for a cool roof. Roberts notes that placing a cool roof over an attic with 10 or 12 inches of insulation will result in only “negligible” additional energy savings. Easley agrees: “Even if you reflect 90% of the heat, that doesn’t mean you’ll reduce your energy bills by that much,” he says, “because the codes already require that you have insulation in the attic.” For homes with air conditioning ducts in the attic, though, cool roofing makes sense, he notes, especially if the ducts leak.
In California, cool roofing materials can contribute to a more efficient roof, as required by Title 24. While there are a variety of methods to increase a roof’s efficiency—by upgrading insulation, for example—most of Los Gatos Roofing’s customers opt to install cool roofs for the extra protection against the heat, notes co-owner Randy Brown.
Sharon O'Malley is a freelance writer in College Park, Md.