How To:

Campervan Insulation


Find lots more details in the NEW Self Build Campervan Conversions book

A nicely converted campervan using foil insulation

1. Introduction - Insulating a Campervan

You’ve made the first step…you’ve acquired a van and now want to convert it to something more luxurious than a tent! First thing, after the planning step of course, is insulation, you might as well keep warm and dry if you’re not sleeping in a tent..! Insulation keeps heat in, excess heat out and reduces condensation. If you splash out on a heater then this combined with a well insulated van will give you the chance to dry out, both yourself and your kit, after a few days of rain.

In a campervan it’s almost impossible not to produce lots of water vapour - everyone in the van breaths, every time you cook something you generate loads of steam - especially pasta etc. So, since there will always be excess water vapour in your van the thing to do is to try to stop as much of the water vapour as possible hitting the cold metal of the van and condensing. The way to achieve this is to create a well insulated room, thereby covering all the metal, with a vapour barrier between the main room and metal whilst doing your best to ensure that your van is well ventilated.

An insulated wheel arch and behind the panel

2. Why insulate a Campervan?

The combination of insulation, a vapour barrier, and ventilation keeps the moist air inside the van warm until it escapes to the outside. The insulation fundamentally keeps the van warm whilst the vapour barrier prevents the water vapour getting to the cold metal condensing.  You want to avoid water on metal wherever you can - recite after me: water + metal = rust! 

When insulating your van remember that ventilation is an equally important part of the equation as this allows the warm moist air to escape out of your van before the vapour has time to condense. Don’t forget that the metal of your van is not the only cold surface, although the hardest to protect against, windows will also give water vapour a cold surface for condensing. Condensation on windows is easily protected against with window insulation mats.

Aluminium van insulation

3. Where to start when insulating...

So, now we know why a campervan should be insulated... but how do you do it?

The main insulating materials available are normal housing insulation (either solid kingspan / celotex type board insulation, or something like glass-wool), thick foam (like thick swimming float material), or foil insulation. Don’t forget that you can use one material by itself or a combination of insulating materials depending on which part of the van you are insulating.

The best combination for DIY van insulation is:

  1. Bare metal
  2. Insulation
  3. Vapour barrier (a sheet of polythene will do, and note if you use the foil stuff you don't need a vapour barrier as it acts like one itself)
  4. Plywood panel or cupboard etc. often covered with lining carpet which also helps with insulation and sound reduction.

The other thing the polythene / vapour barrier does if you're using glass wool is keep all those fibres well sealed away from the air you're breathing.

Foil insulation campervan and motorhome rolls

4. Traditional Insulating Products..?

We would always recommend using a combination approach to insulating your vehicle. Your options being either traditional housing insulation products or foil insulation, here are some pros and cons for you.

Traditional insulation products:

While fibre glass is a very good insulator, and it fits easily into awkward spaces, there are problems with its use. The main issue with fibrous products is that their micro fibres can negatively affect indoor air quality. Not so good if you are sleeping in close quarters to the product, as in a camper, however if you cover it with a vapour barrier or even better with foil insulation, then this is less problematic.  Glass wool is perfect for bunging in all the large cavities that you get in vans, plus it's cheap, so this is a good product to start with.

Solid insulation boards are becoming more and more popular and there is no question they are great insulators, providing you have the space for them.  The main reasons they're not perfect in campervans is often there isn't enough space, and they are rubbish for going round curves, over struts, into small cavities etc.

Foil backed insulation fits easily round corners

5. Using Foil Backed Insulation?

Foil insulation is easy to cut to size and folds easily around difficult shapes like wheel arches. It works by reflecting heat as opposed to things like glass wool which absorbs heat.

The massive advantage of good foil insulation is that it's so thin, easy to work with and works as a vapour barrier - a world apart from either stuffing glass-wool into gaps and then having itchy arms for a week, or trying to cut thick bits of board or foam to fit over awkward bits of the van and then realising your panels won't fit back over the top!

A well insulated campervan

6. Fitting Insulation in your Van

Remove the existing panels on the ceiling, walls, and side and back doors (if they're secured with poppers you can prise them out although some may break so take care).  It is usually fairly easy to stuff glass wool insulation in behind these, then add a layer of campervan foil insulation and replace the panels.   Areas behind units etc can be a little fiddlier.  In some places you can't reuse the original panels as you may need something stronger to secure cupboards to - in that case all you need to do is use the old panels as templates and cut new panels out of plywood.

Foil insulation can be handled and installed without any safety equipment. It moulds easily around irregular shapes (of which there are MANY in vans) and cuts simply with a knife. The insulation can be secured in place using high temperature spray adhesive - it is recommended that a small airspace is maintained between insulation and the finished panels of the vehicle. This provides the space required to reflect heat back into the vehicle. You can also use foil insulation in conjunction with traditional insulations to meet your needs, for example filling a space with glass-wool and then covering that with foil insulation which insulates and acts as a vapour barrier.