After a few trips in the bus with only the thin metal of the bus roof between us and the southern sun, the need for camper insulation was obvious. Typically insulation is for keeping warm in colder climes, but it’s essential for comfort in tropical weather as well – especially in a vehicle whose only “air conditioning” is speeding down the road at 55mph.

We used a combination of ½” thick closed cell foam and radiant barrier to insulate the bus shell prior to installing the camper. The closed cell foam was gym flooring from Costco, and Reflectix brand radiant barrier was used for the innermost layer.

Without diving into the heat transfer properties too deeply, air is one of the best readily available insulators out there. The key to effective insulation is trapping as much air as possible in a given space, and preventing it from moving from one surface to another. In a house, fiberglass insulation is typically used for this purpose, but it has a few downsides for camper applications. It can possibly trap moisture against the metal of the shell and cause rust, or break down into microscopic particles that can become airborne in the enclosed vehicle living space. So in our build, we focused on creating isolated air pockets between the outer shell and inner camper panels to maximize insulation in a limited area without using fiberglass.

The first layer of insulation was the ½” thick closed cell foam. This was adhered to the metal of the shell with 3M Super 90 contact adhesive. Just spray it on the foam, spray it on the shell, push together, and it’s done. This layer instantly made being inside with the sun beating down much more tolerable. Prior to the insulation, you couldn’t hold your hand against the inside of the roof for more than a few seconds in the sun, it was that hot. After just the foam insulation, you could easily touch the foam. The foam was applied to pretty much anywhere the outer layer of sheet metal was accessible from inside. In addition to the thermal insulation properties, it reduced the noise level in the bus considerably by adding a small amount of mass and damping to each panel.

Next up, “dams” of foam were made to separate larger insulated areas into smaller sections.

This should reduce the amount of heat transfer through air circulation. These dams were glued up to the first layer of foam with more spray adhesive.

The final layer used was the radiant barrier, which is essentially an aluminized bubble wrap. The theory is that the stationary air in the bubbles acts as an insulator, and the aluminum layer reflects stray radiant heat back into the air void. This kind of insulation requires an air gap to be effective, and the larger the air gap, the more effective it is. In the case of the bus though, the air gap is limited to the depth of the ceiling. In our build, there is about a 1” gap between the inside surface of the closed cell foam and the radiant barrier. A larger distance would be more effective, but also take away headroom.

The radiant barrier was first glued to the air dams with contact adhesive, then the edges were sealed up with aluminum tape for ducts. This method of installation also provides a vapor barrier between the interior living area and the outer shell, which is important to prevent condensation in the air void, which leads to rust.

Overall, the addition of this insulation drastically improved the livability of the camper interior. Prior to the insulation, it was extremely hot on sunny days, but with the insulation in place it creates a much cooler environment.

The same closed-cell foam and Reflectix method was applied to the roof, doors and side panels.