I was wondering what kind of options I have for insulating either my rock foundation or the floor above it. The foundation is made of large rocks (probably 8"x8"x4" high) and they are 'carved' to fit together. It is a full basement with no insulation neither on the wall or the ceiling / floor above it. How can I insulate this? The rocks go in and out so I can't put a wall next to it easily plus the walls sit inside the wall (the wall is a few inches inside the rock). Any help would be greatly appreciated!
Todd
Answer:
Unfortunately, building a wall inside is about the only way you'll be insulating this because nothing else works as well. I would certainly not insulate the floor/ceiuling cavity. When insulating any below-grade masonry wall it is best to build (in place) a 2X4 structure with studs 16" O.C. and pull it an inch and a half from the wall in order to accommodate R-20 fibre insulation without compressing it. The insulation actually goes from the sub-flooring above to within eight inches of the floor and the 6mm polyethylene vapour barrier goes two inches lower so it can be pinched and stapled to each side of each stud. This keeps the insulation bats from sliding down and at the same time, the system avoids a lot of condensation problems. It also permits a bit of heat loss to the drainage tile along the exterior perimeter of the footings. In areas where frost is a problem, it is important that drainage at this point not be impeded.
