The energy star program specifies minimum solar reflectance low slope.
Roofing with 3 years minimun reflectance.
The requirements apply to new construction and to retrofits or additions that replace or re coat at least 2 000 ft 2 of roof space for nonresidential buildings and 1 000 ft 2 of roof space for.
If you re following iecc you have a couple of options for roof materials.
Owens corning asphalt shingle products labeled as cool are rated with the cool roofing rating council ccrc for solar reflectance and thermal emittance.
Reflectance refers to the roofing material s ability to reflect the energy coming from the sun instead of absorbing it.
Materials lacking 3 year aged tested values for either solar reflectance or thermal emittance shall be assigned both a 3 year aged solar reflectance in accordance with section c402 3 1 and a 3 year aged thermal emittance of 0 90.
The doe uses the low sloped cool roof definition from table 1 and defines steep sloped cool roofs as those with a 3 year aged sri of 29 or greater.
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.
Innate reflectance is measured on a scale from 0 to 1 with the latter being the highest level of reflectivity meaning it reflects 100 of all radiant energy coming in contact with it.
You can install one with a three year aged solar reflectance index sri of 64 or you can instead opt for one with an aged sri of 55 combined with an aged thermal emittance of 0 75 or.
Use roofing materials that have an sri equal to or greater than the values in table 1 meet the three year aged sri value if three year aged value information is not available use materials that meet the initial sri value for a minimum of 75 of the roof area of all new buildings within the project or install a vegetated green roof for at least 75 of the roof area of all new buildings within the project.
Steep slope roofs must have an initial solar reflectance of 0 25.
0 65 initial 0 50 aged.
After 3 years the solar reflectance must be 0 15.
After 3 years the solar reflectance must be 0 50.
A cool roof on residential buildings is defined as one with a 3 year aged solar reflectance of at least 0 20 and an infrared emittance of at least 0 75 or minimum sri of 16 in climate zones 10 through 15 for steep slope applications greater than 2 12 and where the roofing product has a density less than 5 pounds per square foot.
Aged solar reflectance tested in accordance with astm c 1549 astm e 903 or astm e 1918 or crrc 1 standard.
