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.
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.

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.
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.
With the main body insulation in place, there was one final step to insure good, protective (and protected) insulation – a vapour barrier.
I used plastic sheeting from B&Q as my barrier.
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!
