This is a very cool idea....especially for a temporary deal. You could double it up if you wanted. The floor would be the biggest loss at that point.This is just going to sit, right? The factory type insulation for the walls is only 1" thick, and has very little R-value. I think they make the walls and ceiling have a nice "thud" sound to them, but do little to help insulate. Here is what I did when we needed to keep our enclosed trailer heated on a job site. Go to your local commercial construction material place and get some 4x8 -2" or 3"thick sheets of "polyiso" rigid roof insulation and line to inside walls and ceiling with it. I stood them up and used the walls pieces to hold up the ceiling pieces, basically made a box inside the box with no fasteners and easily removed. Worked great, and if you check out some of your local roofers, maybe they have some laying around for cheap.