A designer that we work with from time to time specs 2 layers of 5/8" gypsum wall board (drywall/sheetrock). (He also specs that the vapour barrier be installed between the layers of wall board.)
This does complicate jambs and jamb extensions, as well as electrical boxes. But since walls and ceilings offer more area than just floors, it adds a surprising amount of mass.
Stephen Thwaites Thermotech Fiberglass Fenestration |