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Aug 102009

By Melissa Segrest
Green Right Now

They’ve been around for hundreds of years, but when you think of a metal roof, energy efficiency and attractive, colorful design may not be the first thing that comes to mind.

Forget about the tin roof on Grandpa’s farmhouse. In recent decades, the industry has evolved to the point that metal roofs make up about 10 percent of the residential market share – compared to less than 2 percent in the 1990s.

It is the fastest growing roof product in the residential market, according to Scott Kriner of the Metal Construction Association.

Today metal roofs can be formed to look like shingles, or wood shakes, or even slate and terra cotta tiles. They come in a variety of colors, with infrared-reflective pigments, coatings and textures that offer a rainbow of looks while increasing the roof’s ability to reflect solar heat.

Homeowners have reported saving an average 25 percent on cooling bills with a metal roof, as opposed to asphalt shingles, Kriner said. The savings amount can be  higher in hotter parts of the country. The EPA’s Energy Star program says that cool-metal roofs can reduce peak cooling demand by 10 to 15 percent.

The Energy Star program has guidelines for the types of roofing materials that provide enough energy savings and heat reduction to get their seal of approval. They answer questions about those roofs, and point out that metal roofs and roof-coating products will be more likely to have the Energy Star stamp.

Energy Star says about $40 billion is spent every year in the U.S. to air-condition buildings – which is one-sixth of all electricity generated in a year. In addition to lowered cooling bills, the EPA program’s website points out that a reflective roof may allow a homeowner to buy a smaller and less expensive air-conditioning system. All of that energy savings means fewer fossil fuels are burned.

Another energy-saving aspect of cool metal roofing is created when roofers leave a narrow bit of air space between the roofing panel and roof deck, said Jim Bush, chairman of the roofing council of the Metal Construction Association.

“That space creates a natural airflow which further aids in keeping a home cool, reducing energy needs in the summer months and increasing insulation in the winter,” Bush said. That added dimension to a metal roof makes the roof more energy efficient for northern climates as well as the warmer South.

A study of homes in Florida (conducted by Florida’s Solar Energy Center, and both Lawrence Berkeley and Oak Ridge national laboratories) compared energy efficiency of six identical houses, side-by-side each with different roof materials. White metal reflected 66 to 77 percent of the sun’s energy. The coated, or cool-metal roof, saved 35 percent or more on cooling bills.

In addition to lowering cooling bills, these cool-metal roofs can reduce the “heat-island effect” (particularly in urban areas) that causes air temperatures to remain warmer than they should into the evening, because buildings – especially roofs —  retain heat. Cool metal roofs are efficient not only at reflecting the sun’s heat, but at emitting infrared rays to keep air temperatures cooler.

Beyond energy savings, metal roofers point to a laundry list of advantages:

Metal is lightweight, can be made of recycled material – and can be recycled at the end of its life.

That life, however, is very long. “Typically, most metal roofs carry a 50-year warranty on residences,” said Bush, who is also vice president of sales at ATAS, a large metal roofing and wall systems manufacturer. “We always tell people that this is the last roof they’re ever going to put on their home” especially those homeowners in their late 40s and 50s who have settled into what they hope will be their final home.

Today’s metal roofs don’t corrode, and can withstand hailstorms without a dent, or hurricane force winds. The newer solid sheathing can dampen the noise of pelting rain. Also, metal roofs are good in wildfire-prone parts of the country, because they won’t burn.

All of those advantages mean metal roofs are generally more expensive then their competitors, but, industry insiders point out, their longevity easily makes up the price difference.

And there are federal tax credits (as well as potential state or city rebates) for installing an energy efficient roof – be it metal or not. According to Kriner, the Energy Policy Act of 2005 (along with more recent bills) offer a homeowner a 30 percent tax credit, up to $1,500, for installing a pre-painted cool metal roof with an Energy Star label.

You can learn about some case studies of metal roofs from the Metal Initiative Web site, said Greg Crawford, the executive director of the Cool Metal Roofing Coalition. And, he adds, the Cool Roof Rating Council has information on other state, city or utility district rebates.

For the uninitiated, the most striking difference in today’s metal roofs is the look. With different shapes and colors, they’re difficult to tell from other roofing materials.  The infrared reflective pigments in the paints mean that even dark colors can reflect almost as much as light colors, Crawford said.

“I can be walking down the street and I can tell people, ‘That’s a metal roof,’ and they would never have known it,” Bush said.

For more information on metal roof sustainability and energy efficiency, the Cool Metal Roofing organization has a detailed brochure.

PHOTOS: Courtesy ATAS photo gallery

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