Environmental Benefits of a Metal Roof
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All metal roofing contains a minimum of 25% recycled content and is 100% recyclable at the end of it's useful life. This level of recycled content allows metal roofing to be routinely included on listings for 'green' and recycled content products. In addition, the fact that metal roofs are 100% recyclable means that you will not be adding to the billions of tons of disposed roofing material that is routinely added to our landfills each year.
Lightly coloured, more reflective metal roofing can save homeowners up to 40% in summer cooling costs, as reported by Lawrence Berkeley National Laboratory. You can visit www.roofcalc.com which helps you calculate how much you could save if you installed a metal roof on your home.
A basic unpainted metal roof will reflect much of the solar radiation that would be absorbed by a traditional asphalt roof. Pre-painted metal roofing systems not only reflect solar energy but they also cool the home by re-emitting most of the solar energy that is absorbed.
A cool roof is one that reflects the sun's heat and emits absorbed radiation back into the atmosphere. The roof literally stays cooler and reduces the amount of heat transferred to the building below, keeping the building a cooler and more constant temperature. Imagine wearing a white or a black T-shirt on a hot day. By wearing the white T-shirt you will remain cooler than if you wore a black T-shirt because it reflects more sunlight and absorbs less heat. Cool roofs like a white T-shirt, keep the internal temperature of the building cooler. However, a cool roof need not be white. There are many "cool color" products which use darker-colored pigments that are highly reflective in the near infrared (non-visible) portion of the solar spectrum. With "cool color" technologies there are roofs that come in a wide variety of colors and still maintain a high solar reflectance.
The two basic characteristics that determine the 'coolness' of a roof are solar reflectance (SR) and thermal emittance (TE). Both properties are rated on a scale from 0 to 1, where 1 is the most reflective or emissive.
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Solar Reflectance is the fraction of the solar energy that is reflected by a roof, expressed as a number between zero and one. The higher the value, the better the roof reflects solar energy. For example, white reflective coating or membrane has a reflectance value of 0.85 (reflects 85% of solar energy hitting it and absorbs the remaining 15%), while asphalt has a value of 0.09 (reflects 9%). The Emittance of a material refers to its ability to release absorbed heat. Scientists use a number between 0 and 1, or 0% and 100%, to express emittance. With the exception of a metallic surface, most roofing materials can have emittance values above 0.85 (85%). One example is a metal wrench left in the sun, which is hot to the touch because it has a low emissivity value. |
Solar Reflectance is the fraction of the solar energy that is reflected by a roof, expressed as a number between zero and one. The higher the value, the better the roof reflects solar energy. For example, white reflective coating or membrane has a reflectance value of 0.85 (reflects 85% of solar energy hitting it and absorbs the remaining 15%), while asphalt has a value of 0.09 (reflects 9%).
The Emittance of a material refers to its ability to release absorbed heat. Scientists use a number between 0 and 1, or 0% and 100%, to express emittance. With the exception of a metallic surface, most roofing materials can have emittance values above 0.85 (85%). One example is a metal wrench left in the sun, which is hot to the touch because it has a low emissivity value.
Solar reflectance is the most important characteristic of a roof product in terms of yielding the highest energy savings during warmer months. The higher the solar reflective value the more efficient the product is in reflecting sunlight and heat away from the building and reducing roof temperature. This is particularly important in areas of the U.S. where peak load is a concern.
Emissivity can also contribute to a cool roof. In warm and sunny climates highly emissive roof products can help reduce the cooling load on the building by releasing the remaining heat absorbed from the sun. However, there is also evidence that low emissivity may benefit those buildings located in colder climates by retaining heat and reducing the heating load. Research on the benefits of emissivity is ongoing. Discuss reflectance and emissivity with your roofing contractor to determine what characteristics matter most given your unique climate.
The EPA reports that $40 billion is spent annually in the United States to cool buildings. Ninety percent of the energy in the United States is generated by burning fossil fuels, which create pollution. Therefore, choosing to install a metal roof helps homeowners by saving money on the cooling costs and helps the environment by cutting down on air pollution.
Metal roofing is tested for wind, fire and hail resistance and listed with various building codes and entities. It's non-combustibility can reduce the spread of fire in and among buildings.
Since 1975, the steel industry has invested over $60 billion in new technologies to improve energy efficiency and production. In a typical year, over 15% of the steel industries capital expenditures were directed toward environmental facilities.
This information has been collected from various web sources of metal roofing energy benefits. Please feel free to visit them yourself to find out more information.