Given that, according to the Department of Energy, the average homeowner spends more than $1,000 a year on heating and cooling costs—more than half their total utility expenses—cool roofs are not just smart for the environment, they’re also good for a homeowner’s bank account. They can also go a long way towards helping meet California’s Title 24 mandates. Since many homeowners aren’t hot on the idea of having a white roof, luckily, there are now a variety of methods and products available to increase a roof’s cooling efficiency—from coating it with a high-tech polymer to installing specially

made “cool” shingles or tiles. According to the Cool Roof Rating

Council (CRRC) a cool roof can save a homeowner between 7 and 15% in cooling costs, depending on style. The challenge is deciding which materials are best based on budget, region, and desired aesthetics.

“Cool roofs, which are an average of 50 to 60 degrees cooler, can significantly decrease a home’s AC energy load and, while the materials can cost a slight bit more, the installation costs are the same. So you can see a pretty rapid return on the investment,” says building science consultant, Steve Easley.

The CRRC defines the performance of cool roofs based on two criteria (on a scale from 0 to 1, where products that are closer to 1 perform the best). The first criteria, solar reflectance, quantifies how much of the sun’s energy is reflected by the roof. The other, thermal emittance, measures how well a product releases the heat that it does absorb.

The Solar Reflectance Index (SRI) is a measurement that combines both the solar reflectance and thermal emittance of a surface on a scale from 1 to 100, with 100 being the best performing.

“Ultimately, it’s having a balance of

Cool Roofs–MoreThan Just a Hot TrendJOHNATHON ALLEN

HIGH-TECH COATINGS AND TREATMENTS

GIVE BUILDERS COOL ROOF OPTIONS.

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FEATURE :: COOL ROOFS

MANY OF TODAY’S MOST COST-EFFECTIVE COOL ROOFING PRODUCTS—SUCH AS GAF’S TIMBERLINE COOL SERIES ASPHALT SHINGLES—ARE NOT WHITE, BUT UTILIZE A COMBINATION OF SPECIALIZED COATINGS AND EMBEDDED REFLECTIVE FLAKES TO ACHIEVE A BALANCE OF SOLAR REFLECTANCE AND THERMAL EMITTANCE WHILE ALSO OFFERING A WIDE RANGE OF TRADITIONAL COLORS.

COOL WEATHERED WOOD IS ONE OF FOUR COLORS AVAILABLE FROM GAF’S TIMBERLINE COOL SERIES.

solar reflectance and thermal emittance that matters. Of course, most people don’t want white roofs. So now many companies are offering shingle products that use embedded reflective granules that meet CRRC requirements for a cool roof, but still come in more acceptable colors than white,” says Easely.

GAF’s Timberline Cool series is one relatively low-cost asphalt shingle-style roof that uses enough specially coated reflective granules to qualify as an Energy Star Cool Roof. Owens Corning has also launched a line of uniquely colored cool roofing shingles called the Duration Premium Cool series that meet California Title 24 and initial Energy Star reflective requirements.

According to Easley, builders should visit the product directory on the CRRC’s website (www.coolroofs.org) to determine the best roofing product for their job. “You

especially want to look at the three year aged reflectance value. Most all products will perform well when you install them. The question is, do they still perform well when they age?” he says.

While CCRC measures performance, it does not impose minimum levels. Energy Star, on the other hand, recognizes cool roof products that reduce peak cooling demand by at least 10 to 15%, but does not require third-party certification of performance. To receive the Energy Star label, steep-slope roofing products must have an initial solar reflectance of at least 0.25, and achieve a solar reflectance of 0.15 three years after installation.

In addition to traditional shingles with embedded reflective granules and special coatings, another option involves installing a standing-seam metal roof with a specialized coating such as the

Titan mechanical seam roof, by Custom-Bilt Metals. The Titan system is an Energy Star-rated cool roof solution with numerous colors to choose from that offer SRI values ranging from 87%(white) to 23%(black).

Boral Roofing Company’s LifeTile offers builders a premium cool roof option made of lightweight, long lasting concrete tiles that come in a hand-split cedar shake or slate style and can achieve SRI values of up to 82%, depending on color.

“When you consider the environmental benefits, along with the long term value of lower utility bills, using cool roofing materials makes good sense on any new or remodeled home in a climate where there is AC load for a significant part of the year. Most of the time, it’s just a matter of properly educating builders and homebuyers,” says Easley.

The “coolness” of a roof surface is measured by a combination of both its solar reflectance and thermal emittance. This is defined using the Solar Reflectance Index (SRI), where a standard black roof with a high emittance value of 90%, but a low reflectance value of 5%, would result in an SRI value of 0. Conversely, a white roofing material that is, 80% reflective but has the same 90% emittance capabilities as the standard black surface, would be much cooler and receive an SRI value of 100. You can find out how much a specific home can benefit from installing a cool roof by using the DOE’s handy cool roof calculator, available here: www.ornl.gov/sci/roofs+walls/facts/CoolCalcEnergy.htm

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FEATURE :: COOL ROOFS