Insulation Once you have the electrical wires installed and the hardware attached, it is time to insulate everything. I used 2″ thick Roxul 40 mineral wool. I happened to have a bunch of it on hand, although I would buy it new again if I was doing a new van. Mineral wool is amazing. It is used in high temp furnaces and music studios, and is both thermally and acoustically effective with an R value of 4.2 per inch. It comes in 2’x4′ sheets of various thicknesses and cuts easily with a long blade utility knife. The most common thickness is 2″, but 1″ panels are also available if you need them. Given that the walls of a stepvan are usually 2″ thick, you would…