We’re using several layers of insulation on the van walls and floor. Different products have different insulating properties – either heat or sound insulation – and so we need to use a bit of a sandwich.
The main heat insulation is Thinsulate – pretty much the same stuff as in gloves and coats, but 1-1/2″ thick and specially designed for use in vehicles. It stops noise as well as heat loss. We got this through Hein, another person who has converted a Sprinter van. He couldn’t find a supplier who would sell to him, so he became a supplier and now he sells it to other DIY-ers! He also sells it on Amazon.
Although Thinsulate is pretty good at stopping the van panels (walls, ceiling) from rattling if it’s glued on properly, there are other products that are better at this. We used Reckhorn, which has a butyl based layer to dampen vibration, with a foil layer on top to reflect heat. It only needs around 25% coverage in order to effectively stop rumble noise. There are lots of other products like it out there (Fatmat, Dynamat) but Reckhorn is cheaper and we think it’s as good if not better quality.
We also used Low-E reflective foam for combined heat and noise insulation. It can be used under floors to absorb noise, but when you install it with an air gap, it works to reflect heat back because of its foil layer and closed-cell foam insulating layer. In most places we placed it over the Thinsulate, toward the inside of the van, but in the cab area under the headliner it made more sense to glue the Low-E on first. Reflectix is a better known version of this type of material, but because its middle layer is more like bubble wrap, it doesn’t cut so well, compresses when you stand on it, doesn’t have the same sound insulation properties, and squeaks while you drive. Low-E was a much better option for us.
We even tried to get Thinsulate into the thin gaps inside the ribs and at the sides of the windows. It’s debatable whether the insulation will outweigh the straight conductive heat transfer of the metal, but we had some thin leftover pieces that we could use.
I pulled them through using a wire fish – normally used for pulling wires through walls, here it did a great job of getting the insulation where we wanted it.
Update: Since writing this post, we’ve put together a comparison of all the different types of heat and noise insulation materials that we considered when we chose Thinsulate and Low-E. It covers the relative R-values, costs, and pros and cons of each insulation type.