Insulating a Luton van

Welcome to UKHIppy2764@2x.png

UKHippy is a long running online community and of likeminded people exploring all interpretations on what it means to be living an alternative lifestyle -- we welcome discussions on everything related to sustainability, the environment, alternative spirituality, music, festivals, politics and more -- membership of this website is free but supported by the community.

  • Hello, I'm a longtime lurker here but just signed up to get some advice for doing out a luton box.

    I must have read most of whats been written about insulating vans and the result has been to confuse rather than inform.

    Technical websites that compare the material quality of different insulations talk about XPS, EPS, PIR and PUR.

    In the shop, the choice seems to be expensive foam boards with foil on sold under various brand names (which I think are PIR or PUR based?), cheaper slabs of polystryene (possibly E- or X- PS?), and good old nasty old rockwool.

    My current van is insulated with rockwool that's been in there since the 70's. I say insulated -- the rockwool is good as new in half the van, but anywhere that rain has sneaked in it's a sodden mess. A-okay with the burner going, but crap when it goes out at 4am...

    Part of the reason I'm doing out a new van is that this one is going to be snug as anything :)

    So I guess my question is, what of these polysterene boards? Has anyone given them a go? How do they compare in terms of insulation to the more expensive foam ones? And how does the foam or the polysterene stand up to moisture?

    Pricy foam boards:…rd-1200-x-2400mm/p/190545

    Cheap old polysterene:…mm/p/210823#prodReviewTab

    Many thanks!

  • They are the same item in the link- poly in the link will be thicker than the best insulation for the same thermal quality. It's the black choking smoke that puts me off in the event of a fire and the loss of internal space due to thicker cavity wall insulation. Your saving money by buying a cheaper product but loosing on insulation value or space. If you insulated with hardboard and carpet it would be better than nothing (for a while) then damp, rot and rust becomes a problem. Plus it's not going to be as warm! So it goes, the more you spend, the higher the spec, the better the insulation and the less unnessesary space lost. The Poly sheets they drop in wall cavities when building houses are so think they can stand unsupported. But Thickness isn't really an issue for that purpose within brick walls. Rockwool would probably be as efficient as the poly sheeting and can be compressed to half the thickness. In a truck you need to maintain internal heat, reduce external heat, inhibit the heat from touching a cold internal surface and condensing & Maximise pace. Most vehicles it's touch and go if you can lay accross them or stand up straight without taking 8inches off the internal width and 8inches off of the internal hight (unless your short and have a big truck) not everyone can afford to loose to the thinnest of insulation materials. That spray foam looks fun. If you could get in at it soon after spraying it and morph the still pliable sprayed surface insulation with your hands, to form a interesting surface. Then Spray paint for decor & to seal the insulation. You would evenly insulated your truck to any desired thickness and therefor any thermal rating. I've no idea of the cost but my artistic imagination is running wild. From fake dungeon stone walls to a warm sandy cave environment. Using textured rollers to transform the drying insulated wall surface.
    If you could take your van along to a loft insulating spraying job that contractors were finishing and asked them to tag your job on ££? It's quick, if you have masked down, laid in lighting wires. Even conduits for wires,cables, light fittings, water etc. Anchor any brackets before spraying and you won't run the risk of damaging the thermal properties. If you really wanted the vehicle to last. Simply rust treat and undercoat the entire internal structure with cheap paint before having it spray insulated. I do like the idea of not having to line out/board out a vehicle once insulated so money & time saving too. You can buy DIY spray foam too.

    If it was me I would and will use cellotex, kingspan, spray foam, foil bubble wrap. Rockwool But I wouldn't use the poly sheets.
    I have some poly sheets trapped/sandwiched inside crimped aluminium sheets, about 25 of them. They are interlinking. Made to form a insulated wall on a massive deep freezer room. They are 2'9" wide and 12 foot long. 3/4" thick. Plane smooth white on one side, light inverted vertical ribs on the other side. I bought them secondhand enough to skin and roof a horsebox. That would be the only time I will consider using poly insulation. So your options are many. If you can scout for a deal, a bargain. Get the best you can afford that will work for you.

  • Matt... I'm building a Luton camper at the moment - See the Nora build thread... I've used 2" Celotex throughout, with a decent vapour barrier over the top, and then ply lining... I've got a 1kW oil filled radiator in there to keep it warm, and even on the coldest nights recently - down to minus 6 - that 1kW has kept it around +10 inside..

    Firing up my 2kW burner can get the temp up from 10 to 20 in less than 30 minutes... It's cozy!


  • Thanks all, I fixed the link, it was supposed to show the equlivent size and thickness of foam board. Teachs me to try and be too clever with the links and all.

    Alice, your spray foam fantasies are a bit wild for me. I was going to use the foam to fill all the gaps though.

    It sounds like you're saying the polystyrene is less efficient than the branded foam boards and burns very nasty, the latter being a consideration I had not yet made. Do the foam boards burn less hazzardously?

    You also speculate that rockwoll would possibly be as good as polystyrene at least. I'm actually not opposed to the idea as I'm quite surprised how well the 45yo rockwool and hardboard lineing has fared the frequently moist atmosphere in my current van (provided rain water hasn't gotten to it, on which case both materials are buggered). It seems to bring the benefit of breathability.

    Nutter, you mention your vapour barrier. Is this because you're worryed about moisture damaging the foam boards?

    Thanks for your help,

  • Another vote for celotex and foam to fill the gaps. No vapour barrier though.
    Polystyrene burns easily with black smoke and fumes, and will allow water through.

    Cheap - rockwool in bin bags, tie them up and stack them glued to wall. Will prevent it all sagging, but may still sag in individual bags.

  • ISTR that foam in cans comes in fire grade and normal grade. Don't know what the combustion products are like. What's celotex like for fire/smoke?

    Bags of rockwool is good if you fill - I mean fill - the void, and put enough rockwool inside to hold up for years of being gently vibrated. (not now, Cynthia!)

    Any air gaps allow convection, which is bad both for heat retention and by providing an unobstructed path for falame and hot gases if it all goes wrong.

  • It seems to bring the benefit of breathability.

    breathability = convection = heat losses.


    Nutter, you mention your vapour barrier. Is this because you're worryed about moisture damaging the foam boards?

    Water in the internal air will condense on cold surfaces. So you want the vapour barrier as close to the inner surface as practical, with insulation outside of it.

  • Hi, thank you all for your input. Rick, you advocate celotex and foam without a vapour barrier, brynhyffryd you advocate the barrier.

    If I'm not mistaken (and please correct me), provided the insulation is good and gap-free the moist internal air will never find a cold surface to condense on, vapour barrier or not?

    Rick, how did you hold your vapour barrier up? Screws or staples through it into batons?

    Brynhyffryd, fair point on breathability meaning convection...

  • I dont use one, there are two schools of thought. If you use a vapour barrier you are trying to keep water out, however any gaps will let moist air in which condenses. This then cant get out again and rots your van.
    If you dont put up a barrier you will get some condensation, its inevitable but crucially it is allowed to escape again.

    You have a vapour barrier already, its the walls of your van. Putting up a second one is inviting trouble. In my opinion YMMV.

  • Hey Rick, thanks again for your input. I'm inclined towards the no-inner-vapour-barrier camp, as I don't like the idea of creating a moisture trap.

    Mind you, the luton I've got my eye on is ally skin and frame, so the only thing to rot is the insulation itself.

  • It would appear that some insulation acts like a vapour barrier in the sense of slowing down the transfer of moisture from one environment to another. Eg. Silver backed insulation boards.
    Each vapour barrier comes with its effective working values, some better than others.
    Your lucky if the structure is all Aluminium. Just remember not to use steel screws into the aluminium.
    Here's a list of vapour/moisture barriers.
    Materials used as vapor retarders and values.

    Aluminum foil, 0.05 US perm (2.9 SI perm).
    Paper-backed aluminum.
    Polyethylene plastic sheet, 4 or 6 thou (0.10 or 0.15 mm), 0.03 US perm (1.7 SI perm).
    Advanced Polyethylene vapor retarders that pass the ASTM E 1745 standard tests ≤0.3 US perm (17 SI perm).
    Asphalt-coated kraft paper, often attached to one side of fiberglass batts, 0.40 US perm (22 SI perm).
    Metallized film
    Vapor retarder paints (for the air-tight drywall system, for retrofits where finished walls and ceilings will not be replaced, or for dry basements: can break down over time due to being chemically based).
    Extruded polystyrene or foil-faced foam board insulation.
    Exterior grade plywood, 0.70 US perm (40 SI perm).
    Most sheet type monolithic roofing membranes.
    Glass and metal sheets (such as in doors and windows).

  • 50mm stainless steel self tapping screws are expensive @ £25 for 100apporx (first link I got to) The glues can work out cost effective, not so good if ever you need to remove for maintenance, so get all the wiring done first. Cutting insulation to be a tight fit and taping over joints will not really need further fixing (glueing) the lining boards need fixing to the framework/studding of the vehicle body. Countersunk stainless steel fixings into aluminium. Steel into wood or steel.

  • Apologies for being absent from my own thread, I lost my internet connection for a bit. Thank you all for your input.

    So lets say I'm putting up the more-expensive-but-worth-it foam sheets. I cut them to fit the ally frame in the box, spray foam in the gaps, and put foil tape (this stuff?) over the cracks.

    I recall reading somewhere ages ago that it is considered an error to screw my interior boarding directly to the ally frame because it will rot, and that I should put screw battens to the frame and the boarding to the battens (also permitting greater thickness of insulation). But wouldn't the battens rot as the boarding would?

    Also, I guess that I'm using the foil tape to create a complete moisture barrier together with the foil backing of the insulation boards. If I've got battens screwed to my ally frame with insulation filling the gaps flush with the battens, do I tape over the battens too, putting them on the 'outside' of the vapour barrier?

    Not sure I explained what I mean there very well!

    Thanks again for all your help,

  • If your vehicle roof and seams are water tight. You have reduced any (man made moisture) coming in contact with the cold vehicle sides/roof and there's ventilation in and around the vehicle from time to time, there's no reason to get water between the walls to rot the wood. If you did as you say. Fill with spray any gaps not covered by insulation board. Tape over any seams (not everyone bothers to tape seams) then cover the entire surface with a lining wooden planks, matchboard/sheets/drapes/carpet etc. Your more or less restricting cold air condensing (coming into contact) with a lower surface temperature area. Your screws (made of steel will have little moisture to oxidise and rust.
    If the steel screws enter the aluminium structure. There's a (electrolysis?) electro-blah blah process. That will cause a reaction between the two metals (irrespective) of any moisture. The aluminium will loose the battle in this fight and eventually powder away directly at point of contact with steel screw. Though slowly, something to consider. You could use stainless steel screws to attach the batterns to the aluminium cross members/structure Directly on top of the cross members. This would mean you have the same size gaps to fill with insulation sheets, but can now us a thicker sheet, like you say. Then use (many more) normal steel screws to fix lining board to wooden batterns.

  • First rule when lining a van out...dont screw your lining to the ribs of the van..screw battens to the side of the ribs..then your lining to the battens..otherwise you get a cold cold air outside ..warm air inside..drip.drip.drip.on your screws.

  • Thanks again Alices for going into such comprehensive detail. I understand the box in question is watertight, but I'll make sure of it. And I think you're saying it's fine to have the battens "behind" the tape.

    Good point Spicky, but wouldn't the screws holding the battens suffer the same drippy danger, or is the battern sufficient insulation? Happily the frame of the box is such that the ribs invite filling with spray foam so there shouldn't be cold air hanging around back there.

    Would you glue your foam boards up to the sides or just wedge them in?