I am converting a garage to a winterized workshop. I am putting a wooden floor over the concrete one. When I insulate the floor, would styrofoam or fiberglass be better for the floor, I will be using fiberglass for the walls
Answer:
When installing a floor over a garage concrete floor, about the best results will come after the concrete has been covered with 6mm poly and then 2X4s or 2X? are used as joists under what will eventually be the sub-flooring. This framework of 2” stock has to be raised off the concrete and poly an inch or a bit more so that warm air blown in will be able to migrate to all of the cavity. The best way to accomplish this is with 2X2 blocks no longer than six inches every two feet or so under each joist. Shimming can be done as necessary to get things level. The perimeter of this ‘crawl space’ is now heavily insulated and vapour barriered before sub-flooring is fastened down. Somewhere near one end of this crawlspace a warm air duct blows air in and as far away as possible on the same wall, another opening permits this same air to escape into the return air plenum of the furnace. This will make the floor comfortably warm and there is no other way I know of that will do that at equal or better cost. Depending on the size of the new floor area, one might have to provide more warm air inlets.
