In the process of finishing up the passenger side of the interior, I need to insulate the walls. Before I do that, I pulled the last wiring through the wall cavities. The wall insulation consists of rigid Poly-Iso, separated about 0.5 inch from the skin of the vehicle with a few dots of spray foam, with the Poly-Iso pressed into it. This void acts, both as a barrier and a way to drain any condensation, without wetting the insulation. I add layers of Poly-Iso until there is about one inch space left on the interior side of the wall cavity, which is filled with Denim insulation. I use spray foam to fill any cracks and other areas that are difficult to reach.
Before reinstalling the closet, I add some Formica to its side; the back of the closet receives a single piece of Poly-Iso insulation, that also acts as a black-out material behind the tinted window.
YouTube Link: https://youtu.be/SbU8es9USaI