Insulating a Sprinter camper van conversion

Posted on Thursday, Jan. 28, 2016 in Van Building

Materials List

Material selection

When researching how to insulate the van, it didn’t take long to notice the wild controversy of this topic. And rightly so, I suppose. The selection of materials is dependent on your climate and your camping style. The debate on this topic stems from one thing, moisture causing condensation. If you live in a damp environment and cook inside your van, this will be especially true.

If you’ve ever camped out in a tent on a cold night, you’ve probably woken up in the morning to a shower of condensation dripping from the ceiling. Well, the same thing happens in a vehicle, maybe even worse so given the nature of the metal exterior.

It seems most people agree that if money and mess are no object, then getting the walls sprayed with expanding foam is the best bet. This provides a perfect moisture barrier which will not allow any condensation to form on the inside of the metal surface. But this is expensive.

Cellulose insulation is one everyone seems to agree is a very bad choice. This insulation is made from recycled paper, so you can imagine what a little moisture would do to that.

Fiberglass batting is a material some people say is fine and others disagree. They say that this stuff will quickly deteriorate in a moving vehicle as the glass particles break down into dust. I don’t know if this is true. I believe I read somewhere that the California Sportsmobile shop uses fiberglass in their builds.

I ended up settling on recycled denim batting. While this is not the best for high moisture environments, I live in a desert and thus will not have to worry as much about this. I also planned to stave off as much moisture as possible with a vapor barrier adhered over the top of the wall cavities.

The denim would be used only on the walls where the space allowed for 3-4 inches of batting. For the floor and ceiling, where only one in was available, I wanted to use polyisocyanurate board, or “polyiso” for short. Think of this stuff as top notch styrofoam. It’s basically a sheet form of the expanding spray foam. It is closed cell, so no moisture can flow through it.

In addition to these two materials, I would use a bunch of [Reflectix][] all around to prove an additional radiant barrier.

All of this would easily be held together with heavy duty 3M spray adhesive. Don’t cheap out on this stuff, the lesser grades will let your insulation fall right out of the wall when you’re halfway done with the van.

Down to business

First, I’d like to note that while I of course insulated the floor, I will talk about it in greater detail in another post. For now, I’ll just cover the walls and the ceiling.

I would also like to apologize for the lack of photos through this process. I realized when I was most of the way finished that I needed to stop and document.

Before starting, I made sure all my surfaces were clean and clear of any dirt. I started with the ceiling. The [Reflectix][] insulation comes in a variety of widths. I don’t recall which width I purchased, but just match it to the width between your ceiling ribs.


I started by giving the entire ceiling panel a healthy coat of the spray adhesive and letting it set a few minutes until it becomes tacky. I grabbed an end of the [reflectix][], lined it up to one edge and rolled it out to cover the entire length of that section of ceiling and cut it off flush with a utility knife. Move over to the next panel and repeat.

Reflectix While this photo shows the layers on the floor, they are identical to the ceiling. You’ll notice first the layer of reflectix, then a layer of the polyiso board.

This was an easy one-man job as the adhesive does a great job of sticking the insulation immediately as long as you give it that minute or two to become tacky. The only slightly difficult parts were the section that I had to cut around the roof vent and the front and rear-most sections as they were a little odd sized. Any gaps that I had, I just cut strips of reflectix and glued them in to cover.

I repeated this same process for the walls, but this was far more time consuming to get full coverage. The large panels can be done easily, but it was tedious to cut the reflectix to shape to fit down into the walls around the wheel wells.

I kept applying this stuff until I’d covered every open inch of ceiling, wall and door (and floor too, but again, that will come in another post).

Polyiso board

Next up, attaching the polyiso board to the ceiling, another relative simple job. This is essentially a repeat of how the reflectix was attached, but instead using sheets of 1” thick polyiso board. For this, I actually had to measure each ceiling section, hope out and cut the board to size. I made sure to spray the adhesive well in advance as it needed ample time to become tacky to hold the polyiso board in place.

Ceiling 1
Ceiling 1

I tried to cover all the big flat surfaces first, then filled in any curved sections later with the scraps I had left over. If you live somewhere dry like I do, these little foam particles will be static-clung to everything. I recommend finishing the day with a sweep through with an air compressor, leaf blower, etc.

Ceiling 2
Ceiling 2

You’ll notice in the photos that I also used some of this stuff on sections of the wall. This was only because I ran out of the denim batting and had some polyiso board left over, so I doubled it up and glued it into the wall.

Denim batting

While this stuff isn’t the dangerous type of messy that fiberglass is, it’s still messy in its own right. You’ll probably still want to wear a dust mask or forever have blue boogers.

This stuff is also so easy to work with. I used the same spray adhesive to attached this to the walls. Again, I started with the big surfaces. I applied a healthy dose of adhesive, allowed it to dry a bit, rip off big chunks of the denim batting and stuff it into place. Once I covered all the major wall surfaces, I started tearing the stuff up smaller and fished it through all the ribs and little crevices in the wall.

Again, flush the van out with your wind generator of choice and go take a shower.

Wall 1
Wall 1
Vapor barrier

The hardest part of this whole process was probably the vapor barrier. I used simple plastic sheeting (also called painters tarp, drop cloth) and used foil tape to stick it to the walls. I simply cut big chunks of the sheeting to match the shape of the wall, taped it at the top and worked my way down, flattening and trimming as I went.

Vapor 1 Vapor 2

I realize my vapor barrier isn’t perfect, but my goal was to at least prevent the majority of the moisture. Again, I live and spend most of my time in desert environments, so this isn’t my highest concern. If you live in a wet climate, I recommend spending a little more time here.

Sound dampening

I debated for days on whether I should use sound dampening materials like Dynamat. I eventually decided not to due to costs.

The idea behind this stuff is you cover a big percentage of any flat surfaces and it will prevent sound vibrations from carrying through the large body panels. On my next van, I may consider it again, but so far I’ve been happy with the noise level in my van while traveling down the highway. I think in lieu of spending hundreds on sound dampening the rear, I could better spend my time sealing and sound dampening the front doors, firewall, cab floor, etc.