One of the first things to do when it comes to converting a panel van into a camper is to insulate. I found there to be a lot of information online, some good, some bad and most of it based on the opinion of the poster. I set out to find why we insulate the van and the best methods of insulating when it comes to a camper conversion.

Why do we insulate the van?

Well it’s obvious, isn’t it? We insulate the van to keep us warm while we’re inside, right? Well not entirely. The goal of insulation is obviously to keep heat within the vehicle when it’s cold, however during warm periods, insulation also works to keep excess heat out of the van. Another, often overlooked, reason for insulation to prevent moisture build-up within a camper van’s structure.

What is moisture build-up and how do we prevent it?

In order for the moisture within the air to turn back into its liquid form, it must go through a process called condensation. Condensation is the process of turning hot moist air into liquid water by cooling the temperate of the gas so that it no longer has the capacity to carry water vapour. 

In terms of your camper van, this happens when the warm moist air comes in contact with the cooler, metal skin of the van and windows. It is commonly seen appearing on the windows after spending some time within the van, even on relatively mild days.

So, how do we prevent the build-up of moisture in a camper van? We need to create a thermal break between the warm moist air and the material of the van. The easiest way I found of achieving this was to use a closed cell foam (closed cell so that it can’t absorb any water) adhered to the skin of the van.

What is u-value?

In order to compare the insulating effectiveness of a material, we need to use a common value and this is where the u-value comes in. A definition of what a u-value is, according to is

U-value is the rate of heat flow (in Watts) through 1m2 of a structure when there is a temperature difference across the structure of 1 degree (K or ˚C)

The result of this means that given 2 materials, we can easily see which of them will be the better insulator as it will have a lower value. Remember, the lower the value, the better the insulator.

What insulation should I use in my camper conversion?

This question is the one I found most difficult to get a straight answer on. It seemed like each article/post/person had their own view on what makes a good insulation material.

The product I used was called thermoliner, which is available from Harrisons Trim Supplies in the UK. This product was ideal as it is closed cell foam which has an adhesive backing on one side and is foil backed on the other, the foil helps to radiate heat back inside the van. In addition to this, it also has a low u-value which is what we want to look for in an insulating material.

It’s important to consider the u-value so that you know you’re getting the best performance from the material, as space within the frame of the van is very limited. In addition to a low u-value, we also need to make sure the material is suitable to be fitted within the framework of the van. This means it needs to be pliable and resistant to moisture.

Common insulating materials used in camper conversion

Glass fibre insulation

This type of insulation has excellent u-values (typically around 0.044W/m²K), second only to PIR board and it can be manipulated into all the areas within the van’s structure, as it has a composition similar to wool.

The downsides are that it can hold water, much like a sponge, which is therefore not good as this will sit against the metal causing corrosion. In addition to this, handling glass fibre isn’t nice, the particles can cause itchiness and breathing problems during and after handling. 

I wouldn’t advice using glass fibre as I wouldn’t want the particles to be hanging around in the van, allowing them to be breathed in. It’s not uncommon for this type of insulation to be used by professional converters, however I feel there are better materials available which would provide similar u-values.

Recycled plastic bottle insulation

This type of insulation is inherently eco-friendly as it’s using recycled bottles while still being able to maintain u-values which are comparable with traditional glass fibre insulation. It’s fairly typical that 100mm of insulation will provide u-values in the region of 0.044W/m²K. As the insulation is made from plastic, it means that it’s not susceptible to rotting or the promotion of mould growth, unlike traditional glass fibre insulation. The composition of this material is similar to wool, so is perfectly suitable for installation into the framework of the van.

Combined with a material that provides a thermal break, this type of insulation will provide you with an ideal solution for you camper conversion insulation.

Foil backed bubble wrap

This seems to be a common choice of insulation for DIY camper van conversion, mainly down to the low cost. However, while it’s advertised as insulation, the idea of it is to provide supplemental insulation rather than be used standalone. The foil does help to reflect heat back into the van, but the bubble wrap doesn’t provide a sufficient u-value when compared to the alternatives. Also, where you cut the bubble wrap, you open up voids where water vapour will be able to condense which means you will end up with water build-up.

Foil backed closed cell foam

As I mentioned earlier, this was the choice of insulation when I built my camper van. The reasons I chose it was due to the fact it was self-adhesive, which meant I could easily attach it to the metal skin of the van without having any voids where the moist air would condensate. As it was closed cell foam, it also meant that it couldn’t absorb any water that did find it’s way into the frame of the van, which meant that water couldn’t sit there eventually corroding the metal and causing rust. Finally, as it is a dense foam, it will have a reasonably low u-value.

PIR insulation board

Often known by the brand names Kingspan, or Celotex, these proper names for this type of insulation is PIR board, PIR is short for its chemical name of polyisocyanurate. This is by far one of the most efficient insulation materials that we’ve discussed, with a 12mm board having a u-value of 0.023W/m2K. However, due to its rigidity, the potential use of it is limited to flat surfaces, which within the frame of a van are few and far between.


The ideal solution would be a material that is closely adhered to the outer material of the van, this provides the thermal break, and then another supplementary material which will increase the u-value of the thermal break material to maximise the effectiveness of the insulation.

Whichever material you decide to use to insulate, remember to make sure you minimise the areas where moisture can condense as this will lead to a build-up of water. In time this water will sit against the metal of the van and cause it to prematurely corrode and rust.

Now you know why we insulate camper vans and what materials you should use, how will you insulate your camper conversion? Let me know in the comments and if you have any other ideas, let me know below!


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