Polystyrene Insulated Sheet

My bed in the rear sits in the corner and is tight up against the wall and back of the coach. This past winter, I finally put up a 2 inch board along the whole wall, and the also covered the back window as well. It made a very big difference, as I could actually sleep touching the wall. I did find that you have to seal the edges, otherwise there will be a small circulation of air that bleeds around the outside. I've been camping over Christmas for the past 12 years. It is not uncommon to hit single digits at night. While the coach was always warm, the cold radiated off the windows, so there would be cold spots in bed. Yes, it is well worth it.