Residential Roofing Solar Reflectance Index

Sri measures the roof s ability to reject solar heat defined such that a standard black reflectance 0 05 emittance 0 90 is 0 and a standard white reflectance 0 80 emittance 0 90 is 100.

Residential roofing solar reflectance index.

This measure is calculated from the tsr and te. It is defined so that a standard black reflectance 0 05 emittance 0 90 is 0 and a standard white reflectance 0 80 emittance 0 90 is. The sr value is a number from 0 to 1 0. Incorporates both solar reflectance and thermal emissivity in a single value.

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. For an asphalt roofing shingle to be classified as a cool under the energy codes it needs to have a cool roof rating council crrc rating for thermal emittance and solar reflectance. Solar reflectivity r solar reflectance index sri by color. Solar reflectance index sri.

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. 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. 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. A value of 0 indicates that the material absorbs all solar energy and a value of 1 0 indicates total reflectance.

By lessening the demand for energy it decreases carbon emissions that cause pollution. The third metric used to measure the performance of cool roof coverings is called the solar reflectance index sri. The us department of energy defines the solar reflectance index sri as a measure of the roof s ability to reject solar heat as shown by a small temperature rise. The attic under the roof.

Sri measures the roof s ability to reject solar heat defined such that a standard black reflectance 0 05 emittance 0 90 is 0 and a standard white reflectance 0 80 emittance 0 90 is 100. Furthermore it doesn t store as much thermal energy as an ordinary roof. The guide to choosing a cool roof. For example a standard black asphalt shingle would have an sri in the low single digits.

Another method of evaluating coolness is the solar reflectance index sri which incorporates both solar reflectance and emittance in a single value. It also must meet the specific solar reflectance thermal emittance and or solar reflectance index values defined by the specific energy code.