Solar Reflectance/Emissivity Values

Guest User
5/12/2002
I am planning new construction with a metal roof (corrugated, standing seam or 5V). General concensus, as supported by the data on this website, is that a white metal roof gives better summer thermal performance than a dark roof. Asthetically, I think a white roof looks industrial and will not fit in the style of the home. If we use a mill finish or another color painted roof, how much of the energy saving benefit am I losing. I know that surface texture (gloss vs matte finish) can play a big part in the thermal characteristics. In short, do you have, or can you direct me to some hard data on solar reflectance or emissivity values of different finishes of metal roofs.
Todd Miller
Classic Products, Inc.
5/13/2002
George, There is currently a lot of study and research being given to the energy efficiency of roofing materials and roof systems. Much of this has focused on reflectivity and energy efficiency. Here are some sites where much of this test data can be found: Florida Solar Energy Center: http://www.fsec.ucf.edu/ Oak Ridge National Laboratory: http://www.ornl.gov/ Additionally, many metal roofing manufacturers will have results of tests they have had run on their products. Just contact individual manufacturers for their proprietary information and energy data. There is no place to go where you can find a wide comparison of various metal products and coatings. We do know that there are several variables which affect the overall efficiency of any metal roof system. However, in all tests I have ever seen comparing metal to other types of roofing materials, metal has performed extremely well. One recent development along these lines consists of new reflective pigments which allow for good reflectivity even in dark colors. Some manufacturers have begun introducing these to their metal roof systems. Despite all of this talk of reflectivity, however, let's not lose sight of the fact that there are other factors as well. Some metal roof systems have good built-in airspace between the metal and the roof deck or structure. This can really enhance efficiency as well. Also, metal's ability to be installed over existing roofs helps its overall thermal mass and energy efficiency. There are also radiant barrier films which can be used with many metal roof systems to provide even greater efficiency.
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