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.

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how to insulate your campervan conversion with thermal insulation board

8 thoughts on “Insulating a van conversion”

  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!

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