Solar Reflectance Of Roofing Materials

The solar reflectance index sri is a measure of the constructed surface s ability to reflect solar heat as shown by a small temperature rise.

Solar reflectance of roofing materials.

To meet leed requirements a roofing material must have a sri of 29 or higher for steep slope 2 12 roofing and a sri value of 78 or higher for low slope roofing. It is defined so that a standard black surface reflectance 0 05 emittance 0 90 is 0 and a standard white surface reflectance 0 80 emittance 0 90 is 100. The solar reflectance index is used for compliance with leed. All roofing products must be certified and labeled according to the cool roof rating council crrc to comply with the standards.

Solar reflectance and thermal emittance are the two key material surface properties that determine a roof s temperature and they each range on a scale from 0 to 1. The ages solar reflectance and thermal emittance requirements will vary depending on the slope of the roof climate zone and the density of the roofing product. The more waves that are bounced back into the atmosphere the higher the solar reflectance of the asphalt roofing shingle. Solar reflective shingles are designed specifically to reduce the absorption of the suns infrared radiation by reflecting ir rays off the surface of the roof thus not allowing the heat to be transferred to the interior of the structure i e.

Emissivity is a material s ability to release absorbed energy. Heat island effect roof. Asphalt shingles with higher solar reflectance values can achieve energy star certification. Requirements and is calculated according to astm e 1980 using values for reflectance and emissivity.