On a clear day, your roof can be dangerously hot. That's because dark asphalt shingles -- a common roofing choice for homeowners -- absorb sunlight and convert it into heat. Some of that heat radiates into the air, and some transfers into your home. Rather than invest in a roof that may be raising your heating or cooling bills, consider an alternative -- energy-saving shingles.
Your roof doesn't require any electricity, so shingles themselves are not truly energy-efficient. Energy-saving shingles include products made from a variety of materials available in many colors. What these cool roofing materials have in common is both higher solar reflectance and thermal emittance (see References 1, page 1). They heat up less than standard asphalt shingles, transferring less heat into your home and saving you money for air-conditioning. As of 2011, U.S., homeowners who install Energy Star asphalt or metal shingles can receive a tax rebate equal to 10 percent of the materials cost, of up to $500 (see References 2). For Energy Star certification, energy-saving shingles must reflect at least 65 percent of solar radiation, if installed on a low-sloped roof, or 25 percent if installed on a steep-sloped roof. After three years, those percentages may drop, but they must be at least 50 and 15 percent, respectively. (See References 3)
Cool Roof Choices
Manufacturers produce composite shingles that look very much like asphalt shingles. Lawrence Berkeley National Laboratory scientists are developing roof materials that appear darker, but still reflect near-infrared sunlight (see References 1, page 2).
You can also install solar shingles, which use second-generation thin film photovoltaic cells that look much like normal shingles. Installing solar shingles hooked up to an inverter allows you to convert solar energy into electricity for your home. (See References 5)
Cool roofs have the disadvantage of slightly increasing the amount of energy needed for heating in winter in colder climates (see References 1, page 4). As of 2010, scientists were developing innovative coatings that act as thermometers, reducing roof temperatures by as much as 80 percent in warm weather, and increasing roof temperatures up to 80 percent in cold weather.
- Lawrence Berkeley National Laboratory; Cool Roof Q & A (Draft); Ronnen Levinson; July 2009
- U.S. Department of Energy: Tax Credits for Energy Efficiency
- Energy Star: Energy Star for Roof Products: Fact Sheet for Contractors
- American Chemical Society; Global Challenges/Chemistry Solutions Our Sustainable Future: "Smart" Roofs That Can Save Energy; August 2010
- National Renewable Energy Laboratories: Learning About Renewable Energy: Solar Photovoltaic Technology
An award-winning blogger, Jessica Blue has been promoting sustainability, natural health and a do-it-yourself attitude since graduating University of California, Berkeley in 2000. Her work, seen in a wide variety of publications, advocates an environmentally-responsible and healthy lifestyle.
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