Solar Reflectance Index Metal Roofing

A cool metal roof with high solar reflectance and high thermal emittance would have a lower surface temperature as compared to a roof with low reflectance and low emittance.

Solar reflectance index metal roofing.

Sri is a unit developed by scientists at lawrence berkeley national laboratory. 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. The sr value is a number from 0 to 1 0. After 3 years the solar reflectance must be 0 50.

One example is a metal wrench left in the sun which is hot to the touch because it has a low emissivity value. Solar reflectance is the most important characteristic of a roof product in terms of yielding the highest energy savings during warmer months. After 3 years the solar reflectance must be 0 15. Recycled content of berridge metal.

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. In the case of a cool metal roof a lower surface temperature translates into less heat gain into the attic space or living space below the roof. Solar reflectivity or reflectance is the ability of a material to reflect solar energy from its surface back into the atmosphere. Low slope roofs must have an initial solar reflectance of 0 65.

Leed 2 2 sustainable sites credit 7 2 states that to receive one point building owners should use a roof with a solar reflective index sri of 78 over at least 75 percent of the roof s surface for roofs with slopes less than 2 12. Link between energy savings and emissivity. 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. Steep slope roofs must have an initial solar reflectance of 0 25.

It also must meet the specific solar reflectance thermal emittance and or solar reflectance index values defined by the specific energy code. 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. Solar reflectance index sri. The attic under the roof.

Incorporates both solar reflectance and thermal emissivity in a single value. Solar reflectivity r solar reflectance index sri by color.