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COOL ROOFING PROGRAMS AT A GLANCE

Also known as albedo, a measure of a material’s ability to reflect sunlight (including the visible, infrared and ultraviolet wavelengths), expressed either as a decimal fraction or a percentage. A value of 0 indicates the surface absorbs all solar radiation, and a value of 1 represents total reflectivity.
The ability of a material to release absorbed (non-reflected) heat, expressed either as a decimal fraction or a percentage.
A value that incorporates both solar reflectance and emittance in a single value to represent a material's temperature in the sun. SRI quantifies how hot a surface would get relative to standard black and standard white surfaces. It is 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.
A roof surface having a maximum slope of 2 inches rise for 12 inches run.
Draft 2.0 Roof Products Specification will likely add emittance criteria in 2007.
Three years’ exposure (assumed, pending first actual three year exposure data in the summer of 2006).
Requirement for conditioned spaces only.
Roughly equivalent to, for example, 0.65 reflectance and 0.90 thermal emittance, although a number of different combinations of reflectance and emittance can achieve this value.

Characteristics of Common Roofing Systems¹	Solar Reflectance	Emittance	Solar Reflectance Index
Black EPDM	0.06	0.86	-1
Smooth Bitumen	0.06	0.86	-1
White Granular Surface Bitumen	0.26	0.92	28
Dark Gravel on BUR	0.12	0.9	9
Light Gravel on BUR	0.34	0.9	37
White Thermoplastic (Vinyl)	0.83	0.92	104

(1) Lawrence Berkeley National Laboratory Cool Roofing Materials Database