Our building has a combination of sloped roof surfaces, some of which will use a green roof system (at a 3:12 pitch), and the remainder of which will use roof shingles (at a 12:12 pitch). Our question is when calculating roof areas, should we take the projected horizontal areas of the roof (i.e.-the "flat" areas represented on the roof plan drawing), or should we take the actual (sloped) surface areas, which would inherently be larger than the projected horizontal areas. In our case, we have over 50% green roof when calculated by projected horizontal areas, compared with slightly under 50% green roof when calculated by actual (sloped) surface areas.