Vapour Barrier
Upon purchasing an insulating your van you’ll be starting to wonder if you need a vapour barrier, firstly lets delve into what a vapour barrier is and what it can do for your van.
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What is a vapour barrier?
A vapor barrier is a material used for damp proofing. Typically a plastic or foil sheet, that resists diffusion of moisture through the wall, floor, ceiling, or roof assemblies to prevent interstitial condensation.
The vapour barrier itself is basically a tough foil bubble wrap material. We have gone for the double bubble variety which is thicker and easier to work with and it will also give a small boost to the insulation.
Do I need a vapour barrier?
The topic of a vapour barrier, like insulation is very divisive among the van building community. Some say its absolutely pointless and just more money spent, the reasons behind this are:
- You cannot 100% guarantee that there are no gaps.
- It traps moisture in.
I’ve heard I don’t need a vapour barrier
Whilst these are valid points and there may be some mileage in those comments we personally chose to implement a vapour barrier. I realize that we may not be able to guarantee that there are no tears in the barrier or that one wont be accidentally created later and be left hiding behind a wall, but we feel that by implementing a vapour barrir we’ve taken reasonable care to protect the van from spills from inside and any problems with the trims from the outside.
Again there are suggestions that a vapour barrier may cause unnecessary damp to become trapped within the van. Vans are generally created with plenty of drain holes and air gaps in order to dissipate the condensation. obviously when you fill the cavities with insulation you take away some of the ‘air drying’ that would normally occur.
Having started with our van and seeing the amount of damage caused to the walls, floor and existing ply from the leaky trims I would rather try to protect the inner ply walls of my van and furniture from rot and mold. We subsequently sealed up the tops of the trims with a little bit of Sikaflex to stop the water getting in in the first place, but also a wax was put around the pegs that hold the trim on so that if it does get in it will not collect and rot out holes like it did previously. Water will still be able to drain out of the bottom of the trims, should it find itself in there.
Make sure to allow for ‘air gaps’
Probably the most important thing of all when considering implementing a vapour barrier in a van is to ensure that there are adequate air-gaps between the barrier and the walls. We achieved this by making sure our fixing battens for the wall stuck out further than the insulation and barrier, this allows us a 25mm air gap and will definitely help to allow air to circulate and dry any damp found back there.
we have both lived in places that suffered from damp, particularly in the bathroom. The only way around this is to heat and ventilate the area properly. At home we always open a window when cooking and showering and this helps keep damp to a minimum. We plan to do the same with the camper.
What did we use?
There are various different brands and qualities of vapour barrier material, with Reflectix being one of the best and obviously one of the most expensive. We looked for a compromise with the highest quality and lowest price and found a product called ThermaWrap, available from both Homebase and Wickes, it is also available online via Amazon
We bought two different sizes based on what we could get hold of at the time. For our long wheel base sprinter we used the following:
- Floor: 2x (600mm x 7m)
- Walls, Ceiling, Bulkhead & Doors: 5x (1m x 7m)
Our total cost: £158.95
This was placed over the top of our Celotex insulation and secured down with foil tape. The vapour barrier was applied before any ply lining was put on top.
Van wall –> Celotex –> ThermaWrap –> Ply lining
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