Residential Roofing Solar Reflectance

Painting a metal roof can increase its solar reflectance and thermal emittance allowing it to achieve cool roof status.

Residential roofing solar reflectance.

How they can be made cool. Solar reflective shingles. Solar reflectivity or reflectance is the ability of a material to reflect solar energy from its surface back into the atmosphere. Innate reflectance is measured on a scale from 0 to 1 with the latter being the highest level of reflectivity meaning it reflects 100 of all radiant energy coming in contact with it.

Unpainted metals are typically good solar reflectors but poor thermal emitters so they rarely satisfy low slope cool roof requirements. These shingles must have an initial solar reflectance of at least 0 25 and a three year solar reflectance measurement of at least 0 15. Alternatively you can apply cool reflective coatings. The most well known type of reflective surface is the cool roof.

As you re shopping for your new roof look for the tag or label solar reflectance. Owens corning asphalt shingle products labeled as cool are rated with the cool roofing rating council ccrc for solar reflectance and thermal emittance. A value of 0 indicates that the material absorbs all solar energy and a value of 1 0 indicates total reflectance. Residential roofing options include asphalt shingles metal clay tiles and concrete tiles.

Cambridge tm cool colors reflect a percentage. Solar reflective shingles and solar reflective roofing membranes can be an important component in a building system designed to reduce overall building energy consumption and the impact the home or building has on the environment. 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. This is a requirement in some energy codes.

Reflective surfaces are a form of geoengineering. California s building energy efficiency standards for residential and nonresidential buildings title 24 part 6 contains requirements for the thermal emittance three year aged reflectance and solar reflectance index sri of roofing materials used in new construction and re roofing projects. All of these types of residential roofing products are now available with ir reflective color pigments which act to reduce the temperature of roofs and reflect heat away from the home. Meet the prescriptive solar reflectance and thermal emittance requirements according to the 2016 title 24 standards are rated by the cool roof rating council and meet the cool roof requirements of the los angeles green building code find out more about title 24 here.

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. 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.