Solar Reflectance Of Roofing Materials

With the exception of a metallic surface most roofing materials can have emittance values above 0 85 85.

Solar reflectance of roofing materials.

How they can be made cool. Energy star requires an initial sr value of 0 25 or higher for steep slope 2 12 roofs and 0 15 or greater after three years. 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. Roofing shingles and materials plus factory certified roofers including ratings from real homeowners from north america s largest roofing manufacturer.

The more waves that are bounced back into the atmosphere the higher the solar reflectance of the asphalt roofing shingle. One example is a metal wrench left in the sun which is hot to the touch because it has a low emissivity value. 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. Scientists use a number between 0 and 1 or 0 and 100 to express emittance.

A value of 0 indicates that the material absorbs all solar energy and a value of 1 0 indicates total reflectance. Residential and commercial roofing shingles slate roof ventilation roof underlayments asphaltic and tpo roof membranes. The larger these two values are the cooler the roof will remain in the sun. The sr value is a number from 0 to 1 0.

Link between energy savings and emissivity. 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 solar reflectance measurement ranges between 0 0 and 1 0 with 1 0 representing 100 reflectance with no absorption. Reflective surfaces are a form of geoengineering.

Metal roofs are available with natural metallic finishes oven baked paint finishes or granular coated surfaces. Heat island effect roof. Reflective surfaces can deliver high solar reflectance the ability to reflect the visible infrared and ultraviolet wavelengths of the sun reducing heat transfer to the surface and high thermal emittance the ability to radiate absorbed or non reflected solar energy.