Insulating the van

The first major job in any van conversion (other than making the van watertight, structurally sound etc) is the insulation. Good insulation will keep the heat in when it’s cold outside and keep the cool in when it’s hot outside. Theoretically.

Looking at the many other blogs and forums, it’s clear there’s no particularly ‘right’ way to do this, although there do seem to be lots of wrong ways…

In detailing how I insulated my van, hopefully I’ll give pointers and insights into why I did it the way I did.

It doesn’t take a genius to realise that a van body, comprised of fairly thin steel, is not the best natural insulator. In fact it’s a bloody awful one. Standing in the bare metal van with the heat of the British summer sun blaring down on it (around 27 degrees C) you could be coaxed into thinking it was in fact a greenhouse, not what will hopefully be living accommodation.

The first stage of insulation is one that most follow, but the effects of which are quite debated – the use of reflective bubble wrap. In theory, this reflects heat coming from both sides of the van (interior & exterior) as well as providing a small air gap (in the bubbles) to prevent heat transfer. Some, however, debate that, when used with no sufficient air gaps, reflective bubble wrap is a completely false economy. Nevertheless, I pressed on with this first stage of insulation.

The idea of having a material such as reflective bubble wrap directly on the body metal is not just so that it provides the first layer that heat has to penetrate to enter/ escape, but that it will also prevent condensation forming on the bare metal – which could make your insulation material wet and heavy, and mould could grow.



A mistake I made was not having the patience to order reflective bubble wrap which was actually reflective on both sides (which I found out the larger Wickes stores actually sell), so I bought single-sided and did two layers (twice the work, but hopefully twice the insulating power!)

To stick all the insulation I used Wickes solvent free instant grab adhesive. At £1.99 a tube it’s pretty cheap, but you get through it quickly. I must’ve spent about £50 on the stuff! – It’s costs like that that you don’t anticipate.

Before covering the roof with any insulation, I stuck some flashing tape to it which should hopefully act as a sound deadener when it rains heavily (also visible in the previous photo). I left spaces for the window and roof light so I could insulate around them once they had been installed.


Some of the insulation materials I used
The next stage is whatever your main insulation material is going to be. Again, there is an awful lot of debate as to which is best, for what reason(s) and which is worst. There are a number of factors to consider such as how well the material insulates (many have heat ratings), flammability, safety, weight, whether it’ll soak up water, and practicality. Initially I was going to go with an organic wool, as it is a good insulator and not nasty or bad for the environment. I was put off wool however mainly because it is very susceptible to getting damp if any condensation or vapour gets in, which could cause mould to form or insulation to clump and fall down.

In the end I opted for a recycled plastic insulation from B&Q. It’s not the cheapest thing you can buy, and it doesn’t have the best heat rating but it is far less susceptible to getting damp, it’s not as flammable as some materials, it’s recycled (so that’s always a bonus) and it’s not nasty like fibreglass. (I’ve seen a few people using fibreglass insulation in their van builds and I really don’t think it’s a good idea to be in close quarters with a lot of fiberglass; it’s bad for your health if you inhale it and even if you did a thorough job of sealing it off with a vapour barrier, I wouldn’t trust it.) When this layer of insulation was in, I used Duck Tape as a belt and braces measure to keep it held in place.


Sticking the recycled plastic insulation to the reflective bubble wrap

All the recycled plastic insulation glued in place and held with Duck Tape as an extra precaution
Next was to try and insulate the hard-to-reach areas, for instance inside the metal framework that runs around the van. For this I used a Wickes fire rated (non-flammable) expanding foam filler (which, believe it or not, I required identification to buy!)

Something you have to be careful of when piping filler into areas you can’t see is that you’re not going to be blocking up anything vital, such as tucked-away electrics, hinges, access points or (as you can read in bloopers), seat belts.


Expanding foam filler piped into the metal body framework. TIP: start with what seems too little; it’ll keep expanding! if you need more once it’s done, use more
I also put a layer of filler into the bottoms of the rear and side doors before insulating with the recycled plastic insulation so as to fill any more potential gaps where rust had made small holes underneath.

Now the body insulation was done, it was time to decide how best to insulate the roof.

A method of insulation that some people opt to use for the whole of their van is Celotex boards. Often used in housing walls, these boards which come in a variety of thicknesses are supposed to be good insulators, they’re quite pricey though! I bought two large 25mm boards (which were so big I had to pre-cut them to the right sizes in Wickes car park so as to fit them in my hatchback!) which I would use for the roof of my van. My reasoning here was that they were nice and light and would hopefully hold in place defying gravity fairly easily.


Cut up 25mm Celotex boards. Also the roof light pre-installation
In order to roughly fit the Celotex boards around the curvature of the van roof and the sides of the roof, I made incisions with a Stanley knife and snapped the boards in various places. This way, the metallic reflective coating keeps the board from splitting entirely, but the snapped slits enable the board to be bent effectively around any curvature.


Creatively snapping Celotex boards to enable them to fit around curvatures
As with the other insulation, the Celotex was effectively glued onto the roof, but I used Duck Tape as well as a belt and braces measure.

With the main body insulation in place, there was one final step to insure good, protective (and protected) insulation – a vapour barrier.


All the main body insulation in place
A vapour barrier is a non-porous membrane between insulation material and the inside of the van – basically it does as the name suggests – prevents moisture (predominantly in the form of condensation, steam, or water vapour) from getting to the insulation or bare metal van body, so as to stop any condensation forming and being soaked up by the insulation, leading to mould forming or the insulation becoming ruined.

I used plastic sheeting from B&Q as my barrier.


The vapour barrier going up
As I’d seen others do, I began initially by taping my vapour barrier to the van using Duck Tape. I found out that the tape did not in fact hold the barrier in place particularly well though.
Instead I used a hot glue gun which worked perfectly in holding the barrier in place. I used the tape as well, again as another measure.

Cutting the huge 100 square metre plastic sheet to size and putting up all the bits of the barrier was certainly not an easy task, and I needed the help of another person, but it felt great to have finished the first major task in my van build!

All the insulation plus vapour barrier in place, looking a little bit like a scene from American Psycho

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