Riding the 'cool' roofing wave
When Illinois contractor Leon Kohlmeier tries to sell customers on the benefits of applying a flexible coating on their metal roof, he doesn't just talk about how good it will look or how long the roof will last. He tells them that the coating will save money on their annual air-conditioning bill - and just might help save the environment.
Kohlmeier is promoting a relatively new trend in construction called "cool" roofing. The name refers to any roofing material that reflects a high percentage of the sun's rays, keeping the building occupants more comfortable and saving money on energy costs.
"We think it's a great way to promote our product, basically because of the benefits the customer is going to get," Kohlmeier said. "We have a tremendous amount of data showing them the energy savings they will experience."
According to a 1998 study by the American Society of Heating, Refrigerating and Air-Conditioning Engineers, a traditional, dark-shingled asphalt roof absorbs and retains so much energy that its surface is up to 50_C (90_F) hotter than the outside air temperature. That translates into much heavier demands on a building's hvac system.
However, on a roof made of a highly reflective, light-colored material that absorbs less of the sun's rays, the temperature difference is only about 10_C, and the people inside the building stay cooler. Light-colored roofs also more quickly released whatever energy they had absorbed, the study said.
Not an entirely new ideaSuch information is not news to many longtime roofing contractors or residents of hot, humid climates such as Florida, New Mexico and Arizona. Prior to the widespread use of air conditioning, the most popular type of roof in the Sun Belt was white cement tile.
"It kept the people inside cooler, although they didn't know why," said Danny Parker, a principal research scientist with the Florida Solar Energy Center. "Now we know why."
Parker was one of the authors of a 2001 study on the energy efficiency of residential roofing materials. FSEC researchers compared the summer costs of cooling seven identical homes built as part of a Habitat for Humanity project in Fort Myers, Fla.
Six of the homes' roofs were made of a different material: dark gray asphalt shingles, white shingles, white flat tile, white S-shaped tile, terra cotta S-shaped Spanish tile and white metal. On one home, the dark gray shingle roof was combined with a sealed attic and insulation installed on the roof's decking.
The home with the white metal roof consistently used the least energy, researchers said.
"The results of the study clearly demonstrated that white, galvanized metal roofing material saves the most energy as a result of its high reflectance and superior ability to cool quickly at night," said Craig Muccio, conservation program coordinator for Florida Light and Power Co., which commissioned the study.
According to the study, dark gray roofs only reflect 8% of the sun's heat; white shingle and terra cotta tile roofs reflected 24% and 34% respectively; white metal and cement reflected up to 77% of the sun's energy.
Energy savingscovering a 1,770-sq.-ft. home would save homeowners about $130 or 23% on their annual cooling bill.
"It's surprising that something as simple as choosing a different color can make such a difference," Parker said.
Similar results have been reported in FSEC studies of commercial installations of light-colored, coated metal roofs. In 1996 and 1997, researchers tested how adding a white, flexible or "elastomeric" coating to a Cocoa, Fla. strip mall's galvanized, corrugated metal roof would affect the amount of energy used to air-condition the stores below.
Conklin Benchmark Acrylic Roof Coating, a highly reflective acrylic material, was applied to the roofs of six stores. For comparison purposes, the roof over a seventh store was not touched.
The experiment showed the average cost to cool each store dropped by more than 25%, resulting in an annual savings of $150. The cost of applying the coating was $1,375, meaning the mall owners would recoup the investment in less than a decade.
It's those types of statistics that make the metal construction industry eager to promote its roofing products as "cool." A number of industry organizations recently joined together to create the Cool Metal Roofing Coalition, made up of the American Iron and Steel Institute, Metal Construction Association, Galvalume Sheet Producers of North Carolina, National Coil Coating Association and the Metal Building Manufacturers Association.
Changing mindsArmed with research from the FSEC and Berkeley lab on the energy savings metal roofs can offer, Kriner and other coalition members are contacting energy policy boards nationwide to ensure metal gets a seat at the table of energy-efficient building products. However, Kriner said, that sometimes is a challenge.
The city of Chicago is considering an energy code that would mandate roofing products for some projects that radiate away 90% or more of the energy or heat they absorb, commonly referred to as the emissivity factor. While unpainted metals have low emissivity levels, meaning they retain much of the heat they absorb, many coated and painted metals radiate away 80% or more.
Kriner and other members of the CMRC say Chicago's proposal sets the standard so high that all metal would be excluded. They also point out that in colder climates such as the Midwest, many building owners would see their total yearly energy bills drop with a heat-retaining, unpainted metal roof.
"In northern and moderate climates, at certain times of the year, you would want to retain as much energy as possible," Kriner said, because it would make heating the building easier.
Any increase summer cooling bills caused by an unpainted metal roof would more than be made up in lower heating costs the rest of the year, he added, citing a recent study by the Oak Ridge National Laboratory, a U.S. Department of Energy facility in Tennessee.
Many have misconceptionsKriner said it's a sign that more people need to be educated on metal as a cool roofing product. "We're finding a lot of existing myths and misinformation in the trades at all levels."
At a recent architecture association meeting he attended in New York, Kriner said he was shocked at how little attendees knew about metal roofing.
"They thought of (a metal roof) as a barn roof. They had no idea about precoated metal and new technology," he said.
Architects are not alone in their lack of knowledge about metal's cool side. The education process is still taking place at the contractor and manufacturer level, according to Tom Black, executive director of the Metal Roofing Alliance. For many years, both contractors and manufacturer's representatives "were talking about durability and recyclibility, and that's about it," Black said.
Contractors point out those concerns are still No. 1 with most metal roofing customers. Gainesville, Fla. contractor Bill Bryans, president of A. Bartlett Inc., said environmental benefits are "a minor issue that come up occasionally" among his customers.
Black predicts interest among consumers and contractors will increase sharply in the near future.
"I think that right now, the metal industry, like everyone else ... is trying to get a handle on what role metal can play in generating energy savings for the consumer," he said. "I anticipate (metal) becoming much more important as we develop the data to support cool roofing."
Kohlmeier agrees. "It's one if these things that's an education process. As we develop an energy policy in this country, this will be more and more important."