Residential Roofing Solar Reflectance Index

Furthermore it doesn t store as much thermal energy as an ordinary roof.

Residential roofing solar reflectance index.

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. 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 guide to choosing a cool roof. For example a standard black asphalt shingle would have an sri in the low single digits.

By lessening the demand for energy it decreases carbon emissions that cause pollution. Incorporates both solar reflectance and thermal emissivity in a single value. The attic under the roof. 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.

It also must meet the specific solar reflectance thermal emittance and or solar reflectance index values defined by the specific energy code. The third metric used to measure the performance of cool roof coverings is called the solar reflectance index sri. 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. A value of 0 indicates that the material absorbs all solar energy and a value of 1 0 indicates total reflectance.

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. The higher the sri the cooler the roof will be. 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. Solar reflectivity r solar reflectance index sri by color.

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. 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. Another method of evaluating coolness is the solar reflectance index sri which incorporates both solar reflectance and emittance in a single value. Solar reflectivity or reflectance is the ability of a material to reflect solar energy from its surface back into the atmosphere.

This measure is calculated from the tsr and te. The sr value is a number from 0 to 1 0.