I Installed on an enclosed side porch (18 x 7 feet) with a 12-inch uninsulated space between the ground and the floor, not accessible without ripping out the floor, which I didn't want to do. I have two inches of clearance on top of the old floor before it starts to interfere with doorway clearances. In the winter the floor, and the floor and the room itself, is cold despite wall and ceiling insulation, A friend said he had used an eco foil-like product in a similar situation with good results. So, I put in two layers of Eco Foil directly on the old floor and taped all the seams. Then added j1 inch high joists, 3/8 inch plywood subfloor and new 3/4 inch hardwood flooring from Lowes. I'd guess by January I will know if the effort was worthwhile. Even if not, the new hardwood floor is a big improvement over the old existing floor.