Or this sri value roof slope climate zone min.
Low slope cool roof treatment sri.
Unpainted metals are typically good solar reflectors but poor thermal emitters so they rarely satisfy low slope cool roof requirements.
Minimum solar reflectance index value by roof slope.
Use roofing materials that have an sri equal to or greater than the values in table 1.
How they can be made cool.
Low slope roof less than 2 12 slope check applicable box below.
3 yr aged solar reflectance min.
Tapered insulation is the most common method for creating a slope on a low slope roof but frustratingly neither code addresses compliance for tapered systems.
If aged sri is not available the roofing material shall have an initial sri equal to or greater than the values in table 1.
The ages solar reflectance and thermal emittance requirements will vary depending on the slope of the roof climate zone and the density of the roofing product.
The solar reflectance index is used for compliance with leed requirements and is calculated according to astm e 1980 using values for reflectance and emissivity.
In addition the common belief that an average r value is just as good as the code requirements is just that a common belief not a fact.
Commercial cool roof options include bright white membranes and white coatings.
There are different cool roof standards for commercial low slope roofs and residential steep slope roofs.
Emissivity is a material s ability to release absorbed energy.
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.
Department of energy doe has decided to implement cool roofs on all its buildings whenever practicable3.
Sri low slope1 13 15 0 63 0 75 75 steep slope1 10 thru 15 0 20 0 75 16 1 low slope rise to run ratio of 2 12 lower than 9 5 degrees steep slope rise to run ratio 2 12 9 5 degrees or more table 1 residential cool roof.
Install compliant cool roof material that is listed in the cool roof rating council crrc rated product directory 0 63 aged solar reflectance 0 75 thermal emittance or an sri of 75.
Residential roofing options include asphalt shingles metal clay tiles and concrete tiles.
Low slope roofs require an initial sr value of 0 65 or higher and 0 50 or greater after three year.
Wrapping it all up.
Roof area covered by building integrated photovoltaic panels and solar thermal panels.
Alternatively you can apply cool reflective coatings.
Cool roof requirements for residential and non residential now apply to low slope and steep slope roofs.
