If your roof has multiple pitches and material types, you can use a “weighted- area SRI” value, using "Equation 1" as follows from the LEED Reference Guide. See the Roof Weighted Average Calculator in the Documentation Toolkit for more examples and to see if your roof complies.   

Why are sloped roofs treated differently? A surface absorbs more energy from the sun when it is parallel to the ground plane. In the summer months when the heat island effect is more of a problem, the sun is nearly overhead, and flat roofs are in a position to absorb more heat, so it’s more important for them to have a higher SRI value.

Sloped roofs have different minimum SRI requirements because of the different angles at which the sun’s rays will hit the roof. For example, flat roofs receive more of the sun’s rays at direct angles, thus the SRI requirement for flat roofs is higher (i.e., for lighter material) than for sloped roofs. (See chart, from the credit language.)

The “solar reflectance index” or SRI is the measure of a surface’s ability to reflect solar heat. Higher reflectivity is desirable, because it helps combat the urban heat island effect. SRI can range from zero to over 100, with darker surfaces closer to zero and lighter surfaces approaching 100.

Option 1: Light-Colored Roofing Material on 75% of the Roof Area

Most projects choose to go with a light-colored roof because there is less maintenance and upfront costs. However, low-rise buildings in particular (in which the roof is relatively important in maintenance and cost considerations) should consider the life-cycle cost benefits of green roofs, due to improved insulation and better roof durability.  

Determine the square footage of the roof needed to be light-colored roofing or  a green roof by following one of the options below.

Treat terraces and balconies as roof square footage if they protrude from the building and serve as a roof surface for conditioned spaces below. The top layer over conditioned space counts as a roof. For example, in some high-rise applications a rooftop pool deck will need to factor into equations.  If an architectural covering or balcony does not have conditioned space below, it is counted as non-roof surface covering and is covered under SSc7.1: Heat Island Effect—Non-Roof.

The square footage of a pitched roof should be determined by calculating the surface area of the roofing material itself, not the area as seen from above.

Determine the total square footage of your building's roof surface, then subtract the space taken up by mechanical equipment, such as mechanical rooms for boilers and chillers, HVAC units, PV, skylights and other rooftop systems. The remaining area is the focus of calculations for this credit.