Under the LEED 2009 version, to receive Sustainable Sites Credit 7.2 Heat Island Effect-Roof, at least 75% of the surface of a roof must use materials having a solar reflective index (SRI) of at least 78. This criterion can also be met by installing a vegetated roof for at least 50% of the roof area, or installing a high albedo and vegetated roof in combination that meets this formula: (Area of Roof meeting Minimum SRI Roof/0.75) + (Area of vegetated roof/0.5) ≥ Total Roof Area.