I am insulating the floor of a vented attic in a side-split. This is the attic on the lower side of the house. If you know how a side split is built, then you also know that the attic on the lower part of the house has a wall which is common to the higher side of the house. It is in essence an outside wall. Usually this is next to a bedroom. That room can be quite cold. Insulating the attic floor does nothing for that room since this wall is above the insulation. I am planning to put rigid foam board on this wall. Do I need to cover this foam board to meet firecode.