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The choice of roofing material has the greatest impact on the energy conservation of a home. Cool metal roofs coated with Kynar 500® PVDF based resin can reduce energy consumption by up to 40% as part of a total system design (as reported by the Lawrence Berkeley National Laboratory). Kynar 500 coated metal roofing has many attractive features and benefits. The architectural appeal, variety of profiles, texture and color, flexibility and long-term durability make it popular for residential projects.
 Kynar 500 based painted metal roofing can achieve solar reflectance of over 70%. Reflected solar energy allows the roof surface to remain cooler, which means less heat is transferred into the building. Cool metal roofing coated with Kynar 500 based resin is one way to limit the urban heat island effect.
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| Urban Heat Island - a built environment where the large portion of dark absorbing surfaces such as asphalt paving and dark roof tops trap solor energy and radiate the energy back into the atmosphere. Such areas typically have less vegetation than the surroundings. Urban heat islands can have an air temperature that is 6-12oF higher than the rural suburbs. |
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One way to measure how "cool" is a roof can be with a term called Solar Reflectance Index (SRI). This unitless index is calculated using the solar reflectance value, the thermal emittance value, and a wind coefficient. The SRI calculation can also be used to estimate the surface temperature of the roof product under prescribed conditions. The method for calculating SRI is defined in ASTM E1980-01. Materials with the highest SRI values are the coolest choices for roofing.
A simple SRI calculator is shown below. To calculate SRI, enter the measured solar reflectance value as a decimal, the measured thermal emittance value as a decimal, then click on "Calculate".
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