Residential Roofing Solar Reflectance Index

Installing a cool roof can cut your energy costs while contributing toward a better environment.

Residential roofing solar reflectance index. The higher the sri the cooler the roof will be. A value of 0 indicates that the material absorbs all solar energy and a value of 1 0 indicates total reflectance. The third metric used to measure the performance of cool roof coverings is called the 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.

The sr value is a number from 0 to 1 0. 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. 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.

Furthermore it doesn t store as much thermal energy as an ordinary roof. Solar reflectivity or reflectance is the ability of a material to reflect solar energy from its surface back into the atmosphere. 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.

It also must meet the specific solar reflectance thermal emittance and or solar reflectance index values defined by the specific energy code. This measure is calculated from the tsr and te. 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. 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.

Incorporates both solar reflectance and thermal emissivity in a single value. Another method of evaluating coolness is the solar reflectance index sri which incorporates both solar reflectance and emittance in a single value. 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. 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.

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.