UKH

I’m possibly being a bit dozy, but as I understand it, the van needs insulation, then a vapour barrier, then plywood as the inner wall.

What I’m struggling with is how do you fix the plywood to the van without making holes in the vapour barrier?  

Any attempt so far to find the answer on a van self build type forum or Facebook group ends up in drama and people telling each other how wrong they are.  

If it makes any difference in terms of ventilation etc the bed is in a pop top and the heater will be diesel.  

As I understand it the screw seals the hole it makes in the barrier, check out this guys channel  youtube.com/watch?v=hDZBJw7cV2U&    he has some great videos on van conversion.

Thanks for that

Depending on how thick a ply you intend on using you could always try to bond it on with some quick grip, I'd say you'd be able to bond 6mm ply no worries. But as Glug said the screw would fill in the hole and if you wanted extra confidence you could fill over the top of the screws, the only problem with that is that if you need to remove the ply for any reason it might be hard to finds the screws!!

My build went something like this:

Layer 1 - 2mm silent coat on interior of van outer panel (stops the van exterior panels vibrating whilst traveling so its much quieter)

Layer 2 - recycled plastic bottle insulation (B&Q) or save on type stuff where I needed something a little thinner.

Layer 3 - 10mm of closed cell foam (camping mats)

Layer 4 - vapor barrier (foil coated bubble wrap stuff) sealed together using foil tape

Layer 5 - ply wood with a 2mm adhesive closed cell foam backing. This ensures there's no rattles, seals screw holes and adds extra insulation. I also use a triple layer of foil tape around the edges of the ply to seal it further and it makes the carpet appear a little more seamless where the ply meets metal.

Layer 6 - 4 way stretch carpet 

Maybe all a bit overkill but I wanted to be warm in winter without a heater.

Layer 2 edit: save = dacron

Any space in the van left??

I went with this:

Thermawrap on all internal surfaces.

Recycled plastic rock wool in awkward spaces, Celotex in the square ones.

Cover with more Thermawrap and alu tape over the joins.

Thin wooden batton on to the van chassis through the Thermawrap not worrying about the holes what so ever.

3mm ply mounted onto the batton and covered with stretch carpet. 

I also have some DIY thermarwap window covers and thick curtains, and it feels really cozy with the propex heater going. 

Thanks everyone

Plenty mate, got a 2006 lwb Vito. 3/4 pullout bed. It can sleep 2 for 10 days off grid, only needing water and beer top ups.