With regard to Credit MRc1.1-Exisitng walls, floors and roof: I have a building which has a fake mansard around its perimeter. This fake mansard is outside the building envelope (beyond the face of the walls, mostly above the roof deck). I need to remove a good portion of it, because I am adding onto two sides of the building. Can anyone tell me why I shouldn't exclude the mansard, if I'm retaining almost all of the actual roof deck and more than 50% of the walls?