Insulating a van conversion

Insulating a van

Insulation is one of the most important steps of a van conversion, as without insulation you will get very cold in the winter and very hot in the summer. There is a sea of information about campervan insulation online, and a lot of it is conflicting. When we converted our van we spent a lot of time reading up to decide the best campervan insulation scheme. This post will explain what components you need for insulating a van, and provide a step-by-step guide on how to insulate a van.


Main components needed

  • Sound deadening (to dampen noise such as rain)
  • Thermal insulation board (to fill the large cavities in the van walls)
  • Rolls of wool insulation (to stuff into harder to access nooks and crannies)
  • Vapour barrier (to prevent condensation reaching the insulation)

Prepping your van

Before you start insulating, you’ll need to completely gut your van. This involves taking up any existing floor, removing any lining and patching up any rust. This is always a very nerve wrecking part of the build, as it’s everyone’s worst nightmare to lift up their floor and find it covered in rust! Older Mercedes Sprinter vans can have awful problems with rust, but luckily ours is a 2013 reg and had only tiny spots of rust after cleaning away the dirt. We used some Hammerite ‘direct to rust’ paint to cover these areas before insulating, to ensure the rust wouldn’t spread.

How to insulate your van conversion - girl painting hammerite onto rust on a Mercedes Sprinter camper van

Sound proofing your campervan

Before you start insulating a van, you’ll need to completely gut it. This involves taking up any existing floor, removing any lining and patching up any rust. This is always a very nerve wrecking part of the build, as it’s everyone’s worst nightmare to lift up their floor and find it covered in rust! Older Mercedes Sprinter vans can have awful problems with rust, but luckily ours is a 2013 reg and had only tiny spots of rust after cleaning away the dirt. We used some Hammerite ‘direct to rust’ paint to cover these areas before insulating, to ensure the rust wouldn’t spread.

Before installing any of the insulation, we stuck sound deadening strips to the roof and walls of the van. These are really important to provide sound proofing to your campervan if you don’t want it to sound like a tin can when it’s raining! They take the resonance out of the panels and deaden the sound. We used Silent Coat sound deadening strips which are super easy to apply, and easy to cut to size if you need to use them on smaller panels.

girl sticking sound deadening strips onto a Sprinter van conversion

Insulating a van – floors & walls

We used a mixture of 40mm thermal insulation boards and recycled bottle wool, as there are large spaces that you can fill with the boards, but there are also lots of little hard to reach places that you can fill with the wool.

We chose 40mm Recticel thermal insulation boards as these were thick enough to fill the cavities in the roof and walls between the beams. As we would be battening over the beams anyway, it made sense to us to fill as much of this space as possible. There are a few different brands of thermal insulation board you can buy (Celotex, Kingspan, Recticel) but they all have very similar R values. We went for these over expanded polystyrene board because although it’s more expensive, it has much better thermal properties (a thermal insulation board of 40mm has an R value of 1.8 vs. 1.05 for a polystyrene board).

Cutting these to size is super easy – you can score them to mark out sizes, and then chop them with a saw or bread knife. It’s worth noting that this makes an awful screeching noise!

girl cutting Celotex Recticel thermal insulation boards with a saw

We chose to use recycled bottle wool instead of fibreglass or rock wool as it’s much nicer to work with (it’s not itchy and you don’t need to wear a mask), and it also has the benefit of being much more eco-friendly as it’s made completely from recycled bottles. We ordered ThermaFleece SupaSoft online from the Celtic Sustainables website.

We spent quite a long time stuffing the bottle wool into all of the nooks and crannies in the van. If you don’t do this, it means there are huge areas of empty space in your van that aren’t insulated, so it’s worth spending the time trying to fit as much insulation in as possible, even if this means the slightly tedious task of posting fluff into small gaps with a screwdriver!

man insulating a campervan with recycled bottle wool insulation

Insulating a van – the bulkhead

We built a bulkhead divider between our cab and the back of our van, mainly because of security, and also so that the back of our van would be better insulated. We decided to use 25mm insulation board for the bulkhead so that it wouldn’t eat into the kitchen space too much. As we had built a wooden framework for the bulkhead, it was really easy to slot pieces of insulation into the spaces between the batons.

Insulating a van – the floor

We were super surprised to read that a lot of people put barely any insulation on their floor. As the floor is the place you will lose a lot of your heat from, we went for 40mm thermal insulation boards on the floor. We built a stud work frame with 40mm wide batons which left room to slot the boards into. We worked out that by adding 40mm to the floor we would still have 180cm of height inside our van. As I am a tiny 5″3 and Dale is 5″11, this would mean we would maximise insulation on the floor whilst still both being able to stand up in the van.

Installing a vapour barrier

Once all of the insulation was in place, we then covered the whole van with a huge roll of silver bubble foil insulation. This is basically like bubble wrap made from silver foil. This provides a vapour barrier between the inside of your van where you are breathing, cooking and creating condensation, and all of your lovely insulation. We used several cans of spray adhesive to hold the foil insulation in place, and then taped the seams using aluminium foil tape.

man applying ThermaWrap silver foil bubble wrap insulation to the floor of a van conversion using spray adhesive glue

Now that we’re fully insulated the fun really starts! Next on our list is electrics and building the stud work for the bed and other wooden structures.

Here’s a photo of Ringo completely ‘naked’, and one from after all of the bulkhead and floor insulation was finished.

Thanks for reading, if you have any questions feel free to drop us a message on here or via Instagram!

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how to insulate your campervan conversion with thermal insulation board

27 Responses

  1. Thank you for the post, it’s super useful. I’ve recently bought a VW T4 with a fiver glass pop up added. The previous owners have stuck the foil bubble wrap to the van and then put up plywood. I’ve taken the plywood off and plan to leave the foil, then a layer of wool/ recycled bottles and then wood panelling. Do you think I should put a second layer of the foil bubble wrap over the wool to prevent condensation? Do you think it’s ok to have a layer of foil directly on the van and then insulation over or will this cause condensation? Thanks for any advice.

    1. Hey, glad you have found the post useful. So we would suggest removing the foil bubble wrap that is stuck to the walls of the van, its insulative properties will be pretty poor when stuck directly to the metalwork. The rest of your insulation strategy sounds sensible though: Use a Polyurathane insulation board to fill the large cavities then cram as much recycled bottle wool into all of the gaps. You can then reuse the aluminium foil and stick it over the insulation covering all surfaces if possible. We would also recommend taping the vapour barrier gaps to create a fairly well-sealed insulation cavity. The vapour barrier is one of the most heavily contested areas, usually with people saying “its impossible to fully seal it so what is the point” but from all of the research and calculations we have undertaken in the past few months we are completely convinced of its benefits. Anecdotally, all of the vans we have stayed in that don’t have them get very damp overnight and long term have mould issues etc. In our van, we can do pretty much anything and never see any condensation build-up. Sorry went a bit war and peace on that! Hopefully the advice was useful, good luck with your build!

  2. Hi, I have a factory fit metal bulkhead with a ‘window’ (no glass yet) between the cab and interior. What do you think are the pros and cons of keeping it? I like the security aspect and it would save me building a wooden frame!

    1. Hey Karen, we’d recommend removing the metal bulkhead as these are typically incredibly heavy! We had a metal bulkhead with a sliding door when we bought our van and we removed it for exactly this reason. It’s a better idea to remove it and build a wooden frame to insulate. There is also a second hand market for the metal bulkheads so if you do remove it, you can probably sell it on Gumtree or similar. You could use the metal bulkhead as a template to draw around to onto a sheet of ply to save yourself some time when building the new one. Hope that helps!

      1. Thanks so much! Am loving reading your pages and feel much more confident about the conversion. Have pre-ordered your book too. Will definitely take your advice.

  3. Hi! We have a yellow sprinter too! Ex DHL?
    Just wondering have you done stud work drilled through the vapour barrier after?

    1. Yep, ours is ex-DHL too! Yes, we attached the vapour barrier on top of the insulation, and then screwed battens in on top of this to attach our cladding to. Don’t worry about tiny holes in the vapour barrier from the screws, it will only be subtly affected by these and is hard to avoid!

  4. Hi, I just removed the bulkhead and plan on building my own wooden frame with a slide-down window. I was wondering how wide the slats are you used? 40mm by ?? I also wonder where U attached the framing to the van? I can attach the upper slat to the metal where the bulkhead was fixed and use the floor to attach the bottom slat but where did you attach the vertical slats? is it strong enough to just attach those to the bottom and upper slat?

    1. Hey Thomas, we used 40x40mm battens to build the studwork for our bulkhead so we could put 40mm insulation in the gaps. We attached battens across the top and the bottom, with 4 or 5 vertical battens and a couple of intersecting rows. By the time you’ve ply lined or clad it, that will give it more than enough strength!

    1. Hey – really sorry, we can’t remember exactly how much we used. We just worked out the square meterage of our van interior minus the windows and bought that amount, and it was pretty close to perfect for the amount that we needed! You should be able to do the same to get a decent idea of how much you’ll need.

  5. Heyo!

    Love the site and super helpful posts 🙂

    I was just wondering what you did about flooring after you’d applied the vapour barrier?

    Did you apply some form of flooring straight on top or did you add another layer for a bit of sturdiness, like ply or something?

    1. Hey Ian, glad you’re finding the site useful! It depends what flooring you’re using – we used a 12mm hardwood floor in the van, so didn’t put anything below this as it was already quite sturdy. But if you’re installing a vinyl or laminate it’s probably best to use 12mm ply beneath this, otherwise it will be easy to end up ripping it. You can use a spray adhesive to attach vinyl, but if you’re using a hardwood you can just let it ‘float’ and leave a very small gap at the edges because it can expand. Hope that helps!

  6. This all looks very interesting, and I am going to further explore your site, and add your book to my letter to Father Christmas.
    One question though: I understood that to convert a van in to a camping bus (in my case, an LDV 400), I needed to provide access from the front of the van in to the back. You seem to have completely blocked off access.
    Have I got this wrong, or has the law changed?

    1. Hi Peter, glad you’re finding our website useful! In the UK there are no requirements about having access to the back from the front of the vehicle, and it’s also very hard to get your van officially reregistered as a campervan. This means that most people in the UK can pretty much do whatever they want, as the classification of the vehicle is more about how it looks on the outside, so for example, ours is a ‘van with windows’. However, I’m not sure what the rules are in other countries. Hope that helps!

  7. Hey!
    We have just uncovered nightmare insulation from taking down the roof following a long term leak. I am following your guide (and will be following your book when it finally arrives following Royal Mail misplacing it). I’m hoping to stuff the wee gaps with therma fleece like you guys did but wondering how much you ordered as a rough guide? Many thanks! Sophie

    1. Hi Sophie, oh no what a nightmare! If you don’t receive the book soon please drop us an email at [email protected] and we will get another one sent out for you 🙂 We ordered roughly 1/3 of the total surface area of our walls and ceiling of recycled bottle wool which seemed about right from memory. This is of course assuming that you have a foam insulation board that covers the larger expanses. Hope that helps, good luck!

    1. Hi Hari, unfortunately I don’t remember. You’re best to calculate the surface area of the inside of your van and base it on this – this is what we did. Hope that helps! 🙂

  8. Hi guys,
    Did you leave doors uninsulated ? Have seen something about water needing to flow through doors as factory made, but can’t find details. Many thanks!

    1. Hi Anna, we insulated the doors the same way as the rest of the vehicle – using celotex and recycled bottle wool, and then applied a vapour barrier. You should remove all of the black plastic trim from around your vehicle and seal it with silicone to stop water entering the van, as long as you do this there shouldnt’ be any water flowing through the inside of the door! Hope that helps 🙂

  9. Hiya,

    Really value all the info you guys are putting out there!
    (Also currently waiting to work out exactly what I need and order my electric system with you 🙃!).
    Quick question – I see various different methods of electrics vs insulation. It looks like you did all your insulation first before then installing electrics? I just wondered pros and cons to this, how you managed to keep all the wiring safe without getting compressed by cladding over your vapour barrier?

    Many thanks 🙂

    1. Hi Ally, we always recommend insulating first and then running cables, as this allows you to reach them more easily in case of any issues. We used a few thin vertical battens which we then attached cladding to, so the cables all sit in the gap created by the thin battens. There’s a bit more info in our cladding blog post. Hope that helps!

  10. Hi to you both,
    love the amount of detail you have provided here and in the book, my only question is, what depth celotex have you used ? and have you stuck this to the sides of the van or left a gap? My son has the book but Iam doing most of the work as he works shifts, is it possible for me to get Ebook access or do we have to pay again? Many thanks Trev.

    1. Hi Trev, we used 50mm celotex as this fits in the recesses of the van walls really well. You can fit it into the recesses and it shouldn’t need any spray glue etc as it jams into the space really well! We then used a little bit of tape if required for any large pieces. Hope that helps!

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