SS Credit 7.2: Heat Island Effect: Roof
1 Point
Intent
Reduce heat islands (thermal gradient differences between developed
and undeveloped areas) to minimize impact
on microclimate and human and wildlife habitat.
Requirements
OPTION 1
Use roofing materials having a Solar Reflectance Index (SRI) equal
to or greater than the values in the table
below for a minimum of 75% of the roof surface.
OR
OPTION 2
Install a vegetated roof for at least 50% of the roof area.
OR
OPTION 3
Install high albedo and vegetated roof surfaces that, in
combination, meet the following criteria:
(Area of SRI Roof / 0.75) + (Area of vegetated roof / 0.5) >= Total
Roof Area
Potential Technologies & Strategies
Consider installing high-albedo and vegetated roofs to reduce heat
absorption. SRI is calculated according to
ASTM E 1980. Reflectance is measured according to ASTM E 903, ASTM E
1918, or ASTM C 1549. Emittance
is measured according to ASTM E 408 or ASTM C 1371. Default values
will be available in the LEED for
New Construction v2.2 Reference Guide. Product information is
available from the Cool Roof Rating Council
website, at www.coolroofs.org.
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. It is defined so that a standard black (reflectance 0.05,
emittance 0.90) is 0 and a standard white (reflectance 0.80,
emittance
0.90) is 100. To calculate the SRI for a given material, obtain the
reflectance value and emittance value for the material. SRI is
calculated
according to ASTM E 1980. Reflectance is measured according to ASTM
E 903, ASTM E 1918, or ASTM C 1549. Emittance is
measured according to ASTM E 408 or ASTM C 1371.
Roof Type Slope SRI
Low-Sloped Roof 2:12 78
Steep-Sloped Roof >2:12 29
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