okay..gunna backtrack a bit...original plan was to place foam between 2 x 8 joists with r-20 wool as well with 3/4 ply on top for floor, but was told that moisture would be a problem. Now thought to leave joists open to air and insulate on top of 3/4 ply with foam, and place another 7/8 or 3/4 ply on top. Building will be up on 8 inch cement blocks, with joists 16 OC. Lathe right now about 400 lbs with sandbags...bandsaw will probably be about 300 or so. The rest will be up on benches or from the walls. I ask all this to know if insulating a floor is even necessary in a heated shop, or is it a very necessary step. Building footprint is 16 x 28, but actual shop is 12 x 28 with covered verandah taking up the last 4 feet of depth.