Solar Reflectance Of Roofing Materials

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.

Solar reflectance of roofing materials.

Using solar reflective shingles and solar reflective roofing products that reflect ultraviolet and primarily infrared radiation will reduce damage caused by u v and heat degradation. 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. How they can be made cool. One example is a metal wrench left in the sun which is hot to the touch because it has a low emissivity value.

Metal roofs are available with natural metallic finishes oven baked paint finishes or granular coated surfaces. The sr value is a number from 0 to 1 0. 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.

Scientists use a number between 0 and 1 or 0 and 100 to express emittance. Link between energy savings and emissivity. Unpainted metals are typically good solar reflectors but poor thermal emitters so they rarely satisfy low slope cool roof requirements. A value of 0 indicates that the material absorbs all solar energy and a value of 1 0 indicates total reflectance.

Heat island effect roof. 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. Reflective surfaces are a form of geoengineering. The more waves that are bounced back into the atmosphere the higher the solar reflectance of the asphalt roofing shingle.

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. 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. Asphalt shingles with higher solar reflectance values can achieve energy star certification.