Originally Posted by Faster
I've used Ensolite in the past for this, glued in place, there are some newer less volatile contact cements now too that may not 'eat' foams, and as a inexpensive option the closed cell sleeping pads tenters use can do a decent job too. I don't think you need a lot of thickness for simple condensation prevention.
As well as "regular" contact cement dissolving foam, the fumes are very noxious.
I have successfully used water based contact cement made by 3M. Costs twice as much, but goes twice as far. And non hazardous fumes.