I’ve just bought a lwb relay and it’s just dawned on me I have to face my most dreaded task of insulating the van. All the other bits of a camper conversion I can hack but theres too many conflicting opinions on this.

I’ve read no end of insulation threads all over the net and one on here from 7 years ago but I still haven’t got a definitive answer in my head as for what to do.

Anyone got any success stories? I know I want to make a vapour barrier and I’ll probably go the celotex and silver foil route with some spray foam chucked in the odd hard to reach places.

My plan of attack is:

Sound deaden panels and wheel arches
Silver foil
celotex
silver foil
ply line

Making sure both layers of silver foil are taped and as sealed as I can get them.. however The panels will need to be held on with some batons so not sure how that is going to work as surely there will be holes going though the last silver foil layer so not a “vapour barrier” technically?

I’m not sure on thicknesses of insulation for the floor or ceiling and I’m also not sure if the batons on the floor will just transfer the cold past the insulation making it pretty pointless?

Is it worth silver foiling the floor even?

Just done my mwb Ducato.
Walls first-
Thermawrap on all flat panels as insulation and sound deadening
Silver foil everywhere else
Then recycled plastic bottle insulation in all cavities.
Silver over the top.
Then ply and carpet

Thermawrap on roof in between battening. Will put thermawrap on bottom of roof ply for more insulation and sound proofing

Flow has thermawrap on floor inbetween 9mm ply strips.

Did the same on last van, used silver foil instead of thermawrap to save money. No issues in 8 years….maybe it’s a ball of rust under the conversion!!

whats the difference between thermawrap and silver foil? I thought they were the same thing? Did you worry about a sealed vapour barrier then? Any reason for the plastic bottle ins over celotex?

You don’t realise how much you’re over thinking it til the first night you spend in the van, and end up opening windows as yer too bloody hot, and the condensation is horrendous if ye don’t!.

These are my worries! I’ll be in France all Summer so it needs to be done right

Thermawrap is a sound prouder as well, the cab/engine is so quiet we wanted to try to
Keep the whole van quiet.
Didn’t and haven’t ever stressed too much about vapour barrier. Sunroof is open most of the time for ventilation.
Your van will be hot in the summer – fit a sunroof of you haven’t already!
We use ours a lot and have been happy with the insulation in the last one for all year round use. I don’t like working with celotex and find I can’t stuff it in all the small places.

You don’t realise how much you’re over thinking it til the first night you spend in the van, and end up opening windows as yer too bloody hot, and the condensation is horrendous if ye don’t!.

I really must be using my van differently. We’ve yet to anything to convert it, it’s just a tin ply lined tent and it’s been fine.

No cooking in there but I’d have expected respiration alone to cause problems. In Scotland so heats not a problem.

go remove your ply lining and try sleeping in it.

about 2am i reckon youll get fed up of the dripping from the roof,

the condensation is forming and is being stopped from dripping by your ply lining.

it gets worse if you have living space heating in the van too as your creating a bigger differential in temp.

Silver foil tape is good stuff to keep everything in place seal all joints etc.

the condensation is forming and is being stopped from dripping by your ply lining.

That makes sense, although I’d still have expected to see condensation on the exposed metalwork and glass. Doors open a tad which might make a wee bit of difference.

We’ll see soon enough as the ply lining is coming out for insulation/lining etc.

it gets worse if you have living space heating in the van too as your creating a bigger differential in temp.

Yeh, we don’t have heating either. Just put a jumper on.

fwiw my van was built many years ago by someone that used glassfibre wool

the only place its got damaged was around the aerial and rear rooflite where i had leaks -so i replaced it with more glassfibre wool.

the rest of it is still as youd expect glassfibre wool to be same as it is in my house roof. light fluffy and dry…..and thats in a van which at the time had a 100% humidity level inside and condensated when parked with no one in it…… its now ~60% almost all the time as ive sealed up the leaky roof and dried out the resultant wet ply bed base and dried out the foam.

not my first choice but i do think some people go OTT with the insulation.

yeah jumpers are for camping. i bought mine to be a home on the road for all year round use

condensation will primarily form on the roof because the warm air rises where it contacts teh roof which is cold outside….. meanwhile your ply and air gap also acts as an insulative barrier – try camping in january i expect youll get condensation 😀

Cheers Terry – any reason why you choose gf wool over celotex- ease of insulation? I’m ideally doing mine to be suitable in -20/30 conditions so I can be parked up in the heart of an alpine winter and use it as a home if desired.. which is why I care so much.

i wouldnt chose glassfibre if i was doing it my self.

celotex has a much better U rating than glassfibre. i suspect glassfibre was chosen due to the ease of fitting….

how ever im also not so bothered by it that i would rip it all out to sort it….

i would also be mindful of price. my van stays warm once warm for a long time. we were out in sub zero over night in start of march and the van was never below 10 inside even come morning despite the heating being off all night and it only being 16 when we went to bed. (i have a big thermometor/hygrometer mounted on the wall atm as been monitoring both while it dried out)

so i might use glassfibre again if i was building on a budget.

try camping in january i expect youll get condensation

We have, that’s the bit that surprised me. It might be reduced a bit by the rear door being open allowing ‘some’ condensation to make its way out that way.

I think we’re on different pages in desired levels of comfort. We’re just after a tent with wheels. 😀

well yeah having the door open will replace your warm moist air with cold dry air from outside….its funny how it equalises its self 😀

i have the opposite issue where im at atm in angola where the pisspoor built /insulated buildings leak air con coldness out and the condensation forms on the outside of glass 😀

Don’t mind the cold.

Parked up on the west coast of Scotland in peak midge season. That’s when condensation will be an issue. **** letting those barstads swarm inside the van.

Angola, I thought you was up in the Shire?

i get around. work 35on – 35off at the moment for my sins.

yes i have been there and got that teeshirt sleeping in the back of my previous unconverted van in summer on the west coast with the door open to be able to breathe…..and the midgies coming in

top tip – buy a hanging midgie net for over beds….and secure tat over the rear of your van with the door open.

will give you a fighting chance.

Turns out there’s no issues at all with condensation building between the ply and the roof, on account of there being no ply lining there.

I’m well known for my observation skillz

I’d recommend the foil backed closed cell polyurethane underlay that also serves as a damp proof membrane for concrete floors overplayed with laminate or wood flooring. It is cheap and easy to cut manipulate and fix. After that add any insulation you like.

I used Sonic Gold and as the name suggests it is also good for sound insulation.

I have a 2004 Ducato that was DIY converted when new by a friend who had it for its first 3 years.

Although insulated mostly with the sheet PU foam, it wasn’t particularly well vapour barriered. The area above the cab was particularly bad for a long time as much if the insulation had fallen off behind the head lining. The top of the A-pillar head lining would be wet in the morning. Now sorted with carefully applied thermawrap and polyester wadding.

The point I’m going to make is I had to have the O/S cill replaced as it was rusting through from the inside, I blame mainly condensation collecting down there (not necessarily finding the drain holes).

So
1) Wax the inside of the cills before starting
2) Consider additional ventilation into the large cavity of the those cills. If I convert another ducy I will be putting 3 or so vent grill into the inner cill panels (i.e. below the floor level)
3) Insulate and vapour barrier very carefully.

I’d recommend the foil backed closed cell polyurethane underlay that also serves as a damp proof membrane for concrete floors overplayed with laminate or wood flooring. It is cheap and easy to cut manipulate and fix. After that add any insulation you like.

I used Sonic Gold and as the name suggests it is also good for sound insulation.
this is the exact same stuff i used, makes a lot more sense than the foil bubble crap that does f all for your u/r values…and its gold!

EDIT;
This

How much of a problem is it when you screw through your vapour barrier? I am going to use a wrap of sonic gold between celotex/battons and the ply but I am going to have to screw through. Do I risk rust where the screw penetrates?

Stainless steel screws?

handy.. I actually have a whole roll of that in the attic I bought by accident for some flooring.

So same rules apply – stick it with temp suitable contact adhesive then tape the seams with metal foil (gold side into the van. If I need to baton should I do that first then wrap this over the battons then squeeze in the celotex or are a few holes into the sonic gold from the battons ok ?

steveb – waxoyl wax you mean? and I’m guessing you mean get the vents in from under the vehicle into the cill?

Thanks guys this sounds more sensible. If cost wasn’t an issue would it be wise to use sonic gold then celotex then another layer of sonic gold or pointless?

My take on it is and i could be way off – the ideal would be to cover all the metal with an insulative (is that a word?) layer, leaving no air gaps between it and the metalwork so ideally spray foam. It’s impossible to do this with any other method. Trying to create a 100% sealed vapour barrier is also impossible as holes where rear lights are accessed etc will be a route to the outside skin. Ventilation is the key i think, with a decent air flow from one side of the van to the other ie a window cracked in the front and roof vent in the back.

Was in a place recently looking for some pricing, the described best solution was venting through the top and bottom of the van. So a roof vent and some drop vents. Does that sound about right?

Evidently this fella didn’t really want the business as I never did get a quote despite a reminder.

I agree with twang. The way I see it, essentially you’re putting moisture into the air from breathing, trying to stop it condensing on outer cold surfaces (insulation/barriers) but at the same time you need to get rid of the moisture that builds up inside (ventilation) … the moisture has to go somewhere if it cant condense on a cold surface …

*random thought* … why not have a cold surface area plate designed to catch the moisture that can then drip down and out of the vehicle properly without ??

top tip – buy a hanging midgie net for over beds….and secure tat over the rear of your van with the door open.

Going to order some midge netting from Pennine and get going with the sewing machine.

fisha… that isn’t a terrible idea! I guess it depends what that plate could also be used for in the day to not just make it a waste of space.

I’ve got some “Raptor x” truck bed liner… the back of the van needs painting before the insulation goes in so I’m thinking it maybe worth just truckbed lining the back floor and 6″ up the sides… that way if any condensation does get that far it’ll be sat on plastic and not the van’s floor. I can live with having to redo wood ect.. but if it rots the metal i’d be cheesed.

Sounds like the only place for the vapour barrier to go is on the inside of the van ie after the celotex so holes will be going through it when screwing the ply in place. So I dont know…

I’ve already sorted side windows and a fiamma turbo roof vent to get the airflow.

I’m also going to use some magnets and midge net for the back and side door like mentioned but some nights I just need more stealth and others more warmth!

Sounds like no one really has an ideal solution other than airflow

Done this over the year to my NV400

Celotex/Kingspan – Floor and ceiling 25mm/45mm
Expansion foam so seal it in
Glass wool for the rib/structural cavaties
overlaid by foil bubble wrap stuff
silver tap to seal all that in.
On the SLD and back door )where there is lock gubbins etc) I used the thickest Yoga mats I could find in TK Maxx.
Van is toasty down to -5degC so far this winter 😀

Head on over to here https://www.facebook.com/groups/sbcampervans/ These people seem to know what they’re talking about.

RE putting screws through your vapour barrier I wouldn’t worry too much about that, if you think about it is the same in any building for both the vapour barrier on the inside and the waterproofing on the exterior. Usually you are screwing something into the surface with that screw, i.e a batten, so the fact that you will tighten that up snug against the vapour barrier will keep any gap sealed. Otherwise if you are really concerned then use some kind of rubber gaskets over the ends of your screws?

Just registering an interest here. Gonna buy a LWB Ducato/Relay/Boxer soon hopefully so I have all this joy to look forward to.

Cheers. I was considering putting a small blob of silicone sealant over the top of the recessed screw. Should be easy enough to peel off if I need to unscrew stuff.

Think I’ve pretty much made a decision now based on all the collated advice. Maybe a bit over kill.. but it will put my mind at rest.

Batten the sides and pop in 25 – 50mm of kingspan / celotex to get straight sides, stuck in with expanding foam

Recycled plastic bottle insulation in the ribs / structural cavaties

Stick kingspan / celotex to the roof without battens and stuck with expanding foam – 25mm.

For the floor I’m going to use underlay and cut strips for the deeper bits and then lay wider strips over the top to get it flush – separated with batons and 12mm ply on top. I was going to use kingspan but part of the challenge is to make it sound quieter too and heat rises so hopefully that’ll suffice. (This is probably the bit im most undecided on).. part of me wants to make the floor thinner and increase the thickness of the insulation in the roof.

I’ll probably then have a go at either taping the kingspan / celotex together with aluminium foil or running a super thin plastic sheet. If I run the sheet I’ll use some high temp glue or a pot of rubber to stick it thinly onto the ribs / edges.

Cover in sonic gold or thermawrap and tape with aluminium foil. Where it touches the wooden ribs I may run a bit of rubber or similar where I know the screw holes to be going just to make a tighter seal once nipped up.

Ply line and silicon in the stainless screw heads.

Glue on carpet.

As SBH said I’ll do the closed cell yoga matts to the door bits too.

6mm ply on the sides, 12mm on the floor and 3mm on the ceiling if I can get away with it.

You’ve thought about this quite a bit??
A few tips from my recent insulating which my be worth considering;
Don’t rely solely on the foam for sticking the kingspan, i found that it doesn’t stick that well to the foil surface of the kingspan, i used a combo of foam and stixall, the stixall grabs well and makes life a lot easier too.
I wouldn’t bother with the rubber strip under the battens as the sonic gold is more than ample to seal any holes if that’s what you’re concerned about.
Id also reconciler the floor insulation as in my last van i had 25mm of polystyrene between battens and that was definitely a week part of my insulation, it felt cold to the touch when temps dropped and that was through carpet.
Good luck with the build!

Thanks – I’ve reconsidered due to your experience – I’m going with 25mm celotex under the floor with sonic gold… as well as stixall & foam for holding

Celotex just arrived. Others bits en route.. hopefully get it done in a weekend! wishful thinking maybe.

wishful thinking

Yup.

How ya getting on alexxx? 🙂

Hey Grum – steady progress! Work got in the way tonight but I’ve had a few days on it.

I bought some silent coat sheets and sound deadened all walls, roof, doors – I didnt go overboard but just enough to take the reverberation out of the sheets

It’s got celotex on all the walls / over the cab and back doors – mostly 2x 25mm boards and then I foil taped them sealed. I ended up using gun grade expanding foam to hold the sheets in place. I also used a bit of the foam to fill some ribs I had no intention of gaining access too.

Recycled plastic insulation is in the spaces with big enough holes to poke and get a hand in but too small for celotex.

I basically did 1 side of the van and then pulled all the celotex out and used it as a template for the other.

I had some super sticky foam with a silver backed foil that I found in the garage from my landy project so I used that to seal up the inner sill (after waxoyling it).

One side of the van now has thermawrap on top of it glued on with a temp sensitive spray glue which has been quite good for the motivation as once that is up and taped it starts making the van look like a space again not just a building site.

So going well – just been buying bits and working out where the solar will come into the van, the underslung water and gas tanks ect… which is all chicken and egg stuff and quite tedious!

I’ve got a 40mm vent coming for the roof too before I can crack on with that and really need to decide on a rear reversing camera… but they all appear crap!

So I’m basically in a half finished insulation and half frozen state on what to do next! I think its just going to be a crack on and deal with the problem when you get to it approach.

Side windows are getting fitted next thursday so that’ll be a good step forwards too!

I am taking pics – I’ll try and collate them