I pulled out my camping interior and insulated the van last weekend. My camping interior is modular and came out with a total of 16 bolts.
I used 1" pink foam on the roof. This foam was really easy to work with because it flexed enough to follow the curves. I needed 1.5" foam for the sides and I could only find polyiso in this thickness. Polyiso has a slightly higher R-value but it doesn't bend! I had to slit and break the foam in many places to follow the van curves. I attached the foam pieces with 3M 74. This is formulated specifically for foam and works much better than 3M 77. You can order it online but I'm not sure if you will find it locally. I was fortunate to have a 20 pound tank of the stuff at work, along with a proper spray gun for it!
I filled a number of smaller gaps with expanding foam and trimmed it flush with a razor saw. I also used about 10ft of Thermalite, primarily in the hollow doors. As others have suggested, I was able to easily pull strips of Thermlite into the van ribs, using string.
I skipped Reflectix. It's great at reflecting radiant heat when there's a substantial air gap, but it has little value in conductive applications. I also skipped the vapor barrier. It would have been useful over batting-type insulation, or if there was air behind my foam panels. However, after gluing closed-cell foam directly against the van walls, I don't expect to have moist air back there.
I ordered front window covers from HeatShield. They fit perfectly and they're really heavy duty. Normally, the reflective side faces outward to reflect radiant heat from the sun. I'm going to flip them around backwards during the winter.
Tonight, I'll get started on paneling. I picked up a few sheets of Bubble-X plastic. It's more durable than Coroplast and instead of flutes, it has more of a honeycomb design. It's supposedly available in a variety of colors but my local supplier only had white, which is fine with me. I do plan to decorate my walls with some fun decals.
