Our project uses three different roof systems that contribute to minimizing the heat island effect. Due to the complexity of the roof on this project, calculation of LEED NCv2.2 Credit 7.2 is not entirely clear, as the reference guide offers two formulas for addressing multiple roofing types. Additionally, the building is under an historic preservation easement in the City of Pittsburgh that requires that the pitched roof portion of the building that is visible to the street and passersby be either restored to its original construction, dark slate, or to its most recent construction, asphalt shingles. The first roof system is a vegetative roof that comprises 1,424 sq ft of roof area. The second roof system is a flat roof with a PVC membrane with an SRI of 104 and covers 1,250sqft. The third roof is a steep sloped roof that for the historical reasons above has a faux slate product with an SRI of 8 and covers 1,680sqft. The total roof is 4,354sf, of which 39% is comprised by the historic roof. Due to the number of roofing systems on this project and their differences, no single equation from the LEED NCv2.2 Reference Guide will allow us to appropriately determine the net effect the total roof has on the urban heat island effect. By combining two of the compliance paths already determined by the LEED NCv2.2 reference guide it may be possible to determine one compliance path to cover one project regardless of the complexity of the roof. The reference guide gives four possible compliance paths: Option 1: 75% of the roof surface is required to meet the minimum SRI value for a particular roof type (Area of SRI roof/0.75)>=Total Roof Area Option 2: Vegetative roof is at least 50% of the total roof area (Area of Vegetated Roof/0.5)>= Total Roof Area Option 3: Combine Option 1 and 2 (Area of SRI roof/.75)+(Area of Vegetated Roof/0.5)>=Total Roof Area Option 4: Referenced in the Calculations Section, Weighted averaging to show that the total theoretical roof does comply (Area of Roof A)*(SRI of Roof A/Required SRI)+(Area of Roof B)*(SRI of Roof B/Required SRI)+...>=Total Roof Area To show that the proposed roof of this project does comply with the intent of this credit, the two equations needed would be from \'Option 2\' and \'Option 4\'. The precedent for combining these two calculations comes from \'Option 3\'. Our interpretation on combining different compliance paths is that they can be added together as long as the areas in each equation are independent of one another so that any area on the roof cannot be counted more than once. We propose the following equation for a roof consisting of a vegetative roof along with two or more other roofing systems: (Area of Roof A)*(SRI of Roof A/Required SRI)+(Area of Roof B)*(SRI of Roof B/Required SRI)+...+(Area of Vegetated Roof/0.5)>=Total Roof Area For this and other projects using multiple roof constructions, does the above calculation meet the intent of the credit, and will this be considered an additional path of compliance? Also, is it possible to exclude historic roofs from SS7.2 calculations?