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| Cool Roofs - New Code Requirements |
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 Cool roofs, or high albedo roofs, will be mandatory under new standards for commercial buildings.Cool roofs reflect a large portion of the sun's heat, and have a greater ability to emit, or radiate away, any heat that is absorbed. The ability of a cool roof to perform these functions is measured in terms of solar reflectance (also known as albedo), thermal emittance, and Solar Reflectance Index (SRI). Cool roofs help mitigate the "heat island" effect felt in many big cities, where temperatures may rise 6 to 8 degrees higher than the surrounding countryside, increasing the need for air conditioning, increasing the chances of smog, and making urban areas just uncomfortably hot. Currently, the City of Houston 2008 Commercial Energy Conservation Code requires cool roofs on commercial buildings and multi-family residential buildings over 3 stories, with a roof slope up to 2:12 pitch. The requirement applies to new roofs, additions, building conversions from unconditioned to conditioned space, and certain repairs. The requirements are a minimum solar reflectance of 0.70 and a minimum thermal emittance of 0.75. For the past few years, the only code that addressed cool roofs for projects outside of Houston was ANSI/ASHRAE/IESNA Standard 90.1-2007 for commercial buildings and Standard 90.2-2007 for low-rise residential buildings. Under these standards, cool or "high albedo" roofs, were recognized, but not mandatory. If you had a high albedo roof, you were allowed to use less roof insulation. The new ASHRAE Standard 189.1-2009, Section 5.3.2.3 "Roofs", calls for mandatory cool roofs in climate Zones 1 through 3, which includes the Houston area. The standards calls for minimum initial SRI of 78 for a low sloped roof (less than or equal to 2:12), and a minimum initial SRI of 29 for a steep sloped roof (more than 2:12), or use of U.S. EPA's Energy Star compliant roofing products. This code is considered a "jurisdictional option", meaning becomes enforceable as it is adopted by city ordinances or referenced in other adopted codes, such as the International Green Construction Code (IgCC). The International Code Council's pending International Green Construction Code (IgCC), currently under public review, will require cool roofs in an effort to mitigate heat island effects. Under Section 404.3 "Roof Coverings", for low sloped roofs the minimum aged solar reflectance is 0.55, minimum aged thermal emittance is 0.75, and minimum aged SRI is 60. For steep sloped roofs the minimum aged solar reflectance is 0.30, minimum aged thermal emittance is 0.75, and minimum aged SRI is 25. It is anticipated the final version of this code will be published in 2012. Initial and Aged (3-year) values are used because the Cool Roof Rating Council has recognized that roofing products tend to lose their solar properties over time. So how do you know if your roofing products qualify? A list of roofing products and their solar properties is available on the Cool Roof Rating Council's website at www.coolroofs.org. Cool roof products are available for almost all roof types, including but not limited to rubber, thermoplastic, metal, bitumen, and foam, with various finish coats. For more information, preview ASHRAE Standard 189.1, the IGCC, or the City of Houston guideline. |
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Three Texas Locations
League City, TX (Galveston)
2951 Marina Bay Dr. #130-356
League City, TX 77573
Pasadena, TX (Houston)
3910 Fairmont Parkway #272
Pasadena, TX 77504
Beaumont, TX
2204 Oak North
Nederland, TX 77627