Solar Reflectance Index Metal Roofing

It also must meet the specific solar reflectance thermal emittance and or solar reflectance index values defined by the specific energy code.

Solar reflectance index metal roofing.

The attic under the roof. Low slope roofs must have an initial solar reflectance of 0 65. 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.

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. After 3 years the solar reflectance must be 0 50. 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.

Solar reflectance index sri. 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. A value of 0 indicates that the material absorbs all solar energy and a value of 1 0 indicates total reflectance. One example is a metal wrench left in the sun which is hot to the touch because it has a low emissivity value.

Steep slope roofs must have an initial solar reflectance of 0 25. Only those roof products that meet the specifications. After 3 years the solar reflectance must be 0 15. 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.

Recycled content of berridge metal. Incorporates both solar reflectance and thermal emissivity in a single value. 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. 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.

Sri is a unit developed by scientists at lawrence berkeley national laboratory. Link between energy savings and emissivity.