Our house has an attached garage with a sunroom above it (It's at the back of the house, which is on an incline, so the sunroom is at the same level as the first floor.) The roof of the garage/floor of the sunroom is concrete and the floor is tiled. Not surprisingly, it's quite cold in the winter - the floor is like ice.

I suspect the ideal solution would be to insulate on top of the concrete - between the concrete and subfloor. But that would mean ripping up the tile, which I'd rather not do. The previous owner had made a half hearted attempt to put rigid Styrofoam on the underside of the garage ceiling; about half of the ceiling has insulation.

Would insulating the underside of the concrete floor be a viable solution? I fear trying to keep the big slab of concrete from getting cold in the winter is a futile gesture, and the only real solution is to insulate on the interior of the concrete.

Any thought or suggestions would be appreciated.

- Rich