I’ve insulated four vans, learning about the best insulation for campervans along the way. The first one was a disaster that cost me £600 and left me shivering through a January in the Cairngorms. The fourth? I’m typing this in my pants at 7am in February, and it’s perfectly comfortable.

The difference wasn’t fancy materials or secret techniques. It was understanding what actually works in British weather, where to spend money, and where to save it.

Here’s everything I learned the expensive way, so you don’t have to.

Why Van Insulation Matters in the UK

Let’s be honest — Britain isn’t known for its tropical climate. We’ve got damp winters, unpredictable summers, and more condensation than you’d think physically possible in a small metal box.

Good insulation does three critical jobs:

It keeps you warm. Obvious, but worth stating. An uninsulated metal van is basically a fridge in winter. I’ve woken up to ice on the inside of my windows more times than I care to admit, and it’s properly miserable.

It reduces condensation. This is the big one everyone underestimates. Warm air meets cold metal, and suddenly you’ve got water running down your walls. That leads to mould, rust, and that distinctive damp smell that screams “I live in a van.” Not the vibe you’re going for.

It keeps you cool in summer. Metal boxes heat up fast when the sun hits them. Proper insulation creates a thermal barrier that makes those rare British heatwaves actually bearable.

When it comes to finding the best insulation for campervans, the right materials can make all the difference in comfort and energy efficiency.

Skip insulation or do it badly? You’ll regret it every single night.

The Insulation Types That Actually Work

There’s a lot of nonsense talked about van insulation online. Instagram vanlifers swear by expensive solutions. Forums argue endlessly about R-values. Here’s what matters in the real world.

1. PIR Boards (Celotex/Kingspan) — The Gold Standard

What it is: Rigid foam boards with foil backing, typically 25mm or 50mm thick.

Price: £25-45 per sheet (2400mm × 1200mm) from builders’ merchants

These are what most professional converters use, and there’s a reason for that. PIR (polyisocyanurate, if you’re interested) boards offer the best thermal performance per millimetre of thickness. That matters when you’re working in tight spaces.

I’ve used Celotex in my last two conversions. It’s easy to cut with a sharp knife, fits snugly between ribs, and doesn’t absorb moisture. The foil backing acts as a vapour barrier, which is crucial for stopping condensation.

The downsides? It’s not available on Amazon — you’ll need to visit a builders’ merchant like Wickes, Selco, or Travis Perkins. It’s also rigid, which means cutting lots of awkward shapes for curved van walls. And if you don’t seal the edges properly, you’ll get thermal bridging (cold spots where heat escapes).

Best for: Walls, floor, and roof where you have relatively flat surfaces. Main living areas where thermal performance matters most.

Cost per square metre: £4-8 depending on thickness

2. Armaflex (Closed-Cell Foam) — For Awkward Spaces

What it is: Flexible, self-adhesive foam sheets in various thicknesses (6mm to 25mm).

Check price on Amazon UK — available in pre-cut sheets

This is my secret weapon for all those curved sections, wheel arches, and tight corners where PIR boards won’t fit. Armaflex is closed-cell foam, which means it doesn’t absorb water — critical for a van that’s basically a condensation factory.

It sticks directly to metal with decent adhesive backing (though I always reinforce with contact adhesive in high-stress areas). It’s much easier to work with than rigid boards, and you can build up layers if you need more thickness.

I use 10mm Armaflex for door panels, 19mm for wheel arches, and 6mm for any weird curves or gaps between PIR boards. It’s more expensive per square metre than PIR, so I don’t use it everywhere — just where it makes life easier.

The catch? Lower R-value than PIR for the same thickness. And the adhesive backing isn’t always reliable on dusty or oily metal. Clean your surfaces properly, or it’ll peel off six months later. Trust me on this.

Best for: Doors, wheel arches, curved sections, gaps between other insulation. Anywhere PIR boards don’t fit easily.

Cost per square metre: £8-15 depending on thickness

Get Armaflex from Amazon UK

3. Sheep’s Wool (Thermafleece) — The Eco Option

What it is: Literal sheep’s wool treated to resist pests and moisture, comes in rolls or batts.

Price: £30-50 for a 7.5kg roll from eco suppliers

I’ll admit, I was sceptical about this. Wool in a metal box that gets damp? Sounds like a mould farm waiting to happen. But I tried it in my third van, and it’s actually brilliant for certain applications.

Sheep’s wool is breathable, which means it manages moisture naturally rather than trapping it. It’s also excellent at acoustic dampening — your van will be noticeably quieter. And if you care about eco credentials, it’s about as natural as insulation gets.

The thermal performance isn’t quite as good as PIR per centimetre, but it’s decent. Where wool really shines is in the roof, where you’ve got space and where acoustic dampening makes a real difference when rain hammers down.

The problems? It’s not widely available on Amazon UK (you’ll find some sheep wool insulation options here, but selection varies). It compresses over time, especially in vertical applications. And while it’s treated, you need good ventilation or you can still get moisture issues.

Best for: Roof insulation where you have depth. Secondary insulation layer where you want acoustic benefits.

Cost per square metre: £8-12 for adequate coverage

4. Reflectix / Thermal Foil Bubble Wrap — Overrated Rubbish

What it is: Bubble wrap with reflective foil on both sides.

Available on Amazon UK

Right, controversial opinion time: Reflectix is mostly useless for van insulation.

I see it recommended constantly, especially in American vanlife content. And it does have one legitimate use — as a reflective radiant barrier if you install it with an air gap on both sides. That means battening out your walls, which costs space and money most people don’t have.

Without those air gaps? It’s basically expensive bubble wrap with an R-value of about 1. That’s terrible. A 25mm PIR board has an R-value around 4.5 for comparison.

I wasted £120 on Reflectix in my first van, convinced it would work because everyone on Instagram used it. It didn’t. I froze. Don’t make my mistake.

The only time I use it now: As a vapour barrier behind PIR boards if I haven’t got foil-backed boards. Or for windscreen covers. That’s it.

Best for: Windscreen covers, emergency blankets, making your van look pretty for Instagram while doing bugger all for warmth.

Cost per square metre: £3-6 (still overpriced for what it does)

5. Spray Foam — For Professionals Only

What it is: Expanding polyurethane foam applied with specialist equipment.

Price: £150-300 for DIY kits, £1,500+ for professional application

Spray foam fills every gap and cavity perfectly, creating an airtight thermal barrier. Professional converters love it because it’s fast and effective.

For DIY? It’s a nightmare waiting to happen.

I tried a cheap spray foam kit from Amazon. It expanded more than expected, pushed my wall panels out, and made a sticky mess that took hours to clean. The stuff that landed where I wanted it worked fine, but I wasted half the kit on mistakes and overcorrection.

If you’re getting your van professionally converted, spray foam makes sense. For DIY, stick with boards and foam sheets you can measure, cut, and control.

DIY spray foam kits on Amazon UK — proceed with extreme caution

Best for: Professional converters, filling small gaps and cavities after main insulation is done, people who enjoy chaos.

Cost: Varies wildly, usually not worth the hassle for DIY

6. Acoustic Deadening (Dynamat / Dodo Mat) — Not Insulation, But Important

What it is: Heavy rubber-like sheets that dampen vibrations and road noise.

Check Dodo Mat on Amazon UK

This isn’t thermal insulation — it’s acoustic deadening. But it matters more than you think.

Vans are loud. Engine noise, road rumble, rain on the roof — it’s all amplified by bare metal panels. Acoustic deadening goes directly onto metal before any other insulation, reducing vibrations and making everything quieter.

I use Dodo Mat (cheaper than Dynamat, works just as well) on floors, doors, and the roof. You don’t need 100% coverage — focus on the largest flat panels where noise reverberates most.

Does it provide thermal insulation? Minimal. But it makes your van feel more like a home and less like a biscuit tin on wheels. Worth the investment.

Best for: Large flat metal panels, anywhere you want to reduce road noise and vibration. Apply before other insulation.

Cost per square metre: £5-10

Get Dodo Mat from Amazon UK

My Recommended Insulation Strategy

After four vans, here’s the system I use now. It balances performance, cost, and practicality.

Step 1: Acoustic Deadening (Optional but Recommended)

Cover 30-50% of large flat panels with Dodo Mat or similar. Focus on:

• Roof (especially above sleeping area)
• Floor
• Sliding door
• Rear doors

Cost: £100-150 for adequate coverage

Step 2: Main Insulation

Floor: 25mm PIR boards between battens, sealed at edges Walls: 25mm PIR boards between ribs, gaps filled with expanding foam Roof: 50mm PIR boards if space allows, or 25mm PIR + sheep’s wool layer Doors: 10-19mm Armaflex, easy to fit around window mechanisms

Cost: £300-450 for materials

Step 3: Awkward Bits

Use Armaflex for:

• Wheel arches
• Curved sections
• Gaps between PIR boards
• Door pillars
• Any tight corners where PIR won’t fit

Cost: £80-120

Step 4: Vapour Barrier

If your PIR boards aren’t foil-backed on the interior side, add a vapour barrier. This stops warm, moist air from inside your van reaching cold metal and condensing.

Options:

• 1200 gauge polythene sheet (cheap, effective)
• Reflectix (expensive, but works as vapour barrier)
• Foil-backed insulation boards (built-in barrier)

Tape all seams with foil tape. Don’t skip this — it’s the difference between a dry van and a condensation nightmare.

Cost: £20-40

Total cost for full van insulation: £500-760 if you DIY

Installation Tips

1. Clean Your Metal Properly

Grease, dust, and loose rust will stop adhesive working. I learned this when Armaflex sheets peeled off my door panels three months after installation.

Use panel wipe or isopropyl alcohol. Get it properly clean. It’s boring, but it matters.

2. Treat Rust Before Insulating

You’re about to seal moisture against metal for years. Any existing rust will spread like wildfire under your nice new insulation.

Wire brush or sand any rust back to bare metal. Treat with rust converter. Let it dry completely. Then insulate.

I didn’t do this in van number one. Two years later, I had rust holes in my floor. Expensive lesson.

3. Don’t Create Moisture Traps

Any cavity you create can trap moisture if you seal it completely. This is especially important in the roof, where warm air rises and condensation forms.

Options:

• Leave small ventilation paths for air circulation
• Use breathable insulation (like sheep’s wool) in cavities
• Install ventilation fans (Maxair or Fantastic Fan)

I’ve got two roof vents in my current van — one at the front, one at the back. Creates airflow, evacuates moisture, prevents mould. Critical in UK dampness.

4. Seal Everything

Every gap between insulation boards is a thermal bridge where heat escapes and cold metal is exposed. That’s where condensation forms.

Use expanding foam (the cheap stuff from Screwfix is fine) to fill every gap. Let it cure, trim off excess, seal with foil tape.

Yes, it’s tedious. Yes, it matters.

5. Don’t Compress Insulation

Insulation works by trapping air. Compress it, and you reduce its effectiveness dramatically.

This mainly applies to wool or foam insulation. Don’t squash it behind wall panels or under flooring. Give it space to do its job.

6. Test Before You Seal

Install insulation, but don’t rush to fit wall panels immediately. Wait for a cold night or rainy day. Check for condensation forming anywhere.

Found a problem? Fix it now. Once wall panels are up, you’re committed.

Common Mistakes

Mistake 1: Not Enough Roof Insulation

Heat rises. Your roof is where you lose the most warmth and where condensation forms worst. I used 25mm insulation in my first van’s roof because that’s all I had left. Terrible decision.

Use the thickest insulation you can fit in the roof — ideally 50mm. And seriously consider double-layering with wool for extra performance and acoustic benefits.

Mistake 2: Forgetting the Floor

Cold feet make everything miserable. An uninsulated floor sucks heat out of your van and makes it impossible to get warm.

I insulated my floor properly from van number two onwards — 25mm PIR boards between timber battens, sealed edges, plywood over the top. Massive difference.

Mistake 3: Insulating Over Electrics

I buried wiring under insulation in my first van. When I needed to add a socket six months later, I had to rip out insulation to access cables.

Run all your electrical conduit and wiring BEFORE insulation goes in. Leave service loops at logical points. Thank me later.

Mistake 4: No Vapour Barrier

For two years, I didn’t understand vapour barriers. My van was always slightly damp, and I couldn’t figure out why.

The problem: warm, moist air from cooking and breathing was penetrating insulation and condensing on cold metal behind it. The solution: a proper vapour barrier on the warm side of insulation.

Add this. It’s cheap. It works.

Mistake 5: Insulating Windows

Yes, I’ve seen people try this. Yes, it’s pointless.

Windows are your main source of light and ventilation. They’re going to leak heat no matter what. Accept it. Use thermal curtains or reflective covers at night, and focus your insulation efforts on walls, roof, and floor.

Real Cost Breakdown: My Last Van

Here’s exactly what I spent insulating my current van (LWB high-roof Sprinter):

Acoustic deadening:

• 3 rolls Dodo Mat (20 sheets): £90

Main insulation:

• 6 sheets Celotex 25mm (walls/floor): £180
• 4 sheets Celotex 50mm (roof): £160
• 2 rolls Armaflex 19mm: £75
• 1 roll Armaflex 10mm: £35

Sealing & barriers:

• 4 cans expanding foam: £20
• Foil tape (2 rolls): £15
• Sikaflex (2 tubes): £25

Total: £600

That’s for a large van with acoustic deadening. A smaller van (VW Transporter size) would be £400-500. A basic job without acoustic deadening could be done for £300-350.

Is it worth it? Absolutely. I’ve slept comfortably in -5°C weather. No condensation. No mould. And my diesel heater barely runs because the insulation keeps warmth in.

Frequently Asked Questions

Q: What R-value do I need?

Honestly? R-values are overrated for van insulation. You’re working with limited space and curved surfaces — you’ll never achieve the R-values recommended for houses.

Focus instead on filling every gap, preventing thermal bridges, and using the best insulation you can fit in the space available. 25mm PIR boards (R-value around 4.5) are adequate for UK weather if properly installed.

Q: Should I insulate my van windows?

No. Use thermal curtains or reflective screens at night, but don’t insulate the windows themselves. You need light and ventilation.

Q: Can I use house insulation in my van?

Depends. Fibreglass loft insulation? No — it absorbs moisture and compresses, becoming useless. PIR boards designed for house walls? Yes, they’re the same product. Rockwool? Maybe, but it’s heavy and prone to moisture issues without excellent ventilation.

Q: How do I stop condensation completely?

You don’t. You manage it. Good insulation plus vapour barrier reduces condensation dramatically, but you’ll still get some moisture. Combat it with:

• Roof vents (critical)
• Crack windows when cooking
• Don’t dry wet clothes inside
• Use moisture-absorbing products in winter
• Wipe down obvious condensation daily

Q: Is more insulation always better?

No. You’re balancing thermal performance against:

• Space (thick insulation reduces living space)
• Weight (important for payload limits)
• Moisture management (some insulation types trap moisture if layered incorrectly)

There’s a point of diminishing returns. 25-50mm of good insulation properly installed beats 100mm of crap insulation with gaps and thermal bridges.

Q: Can I insulate my van in winter?

Yes, but with caveats. Some adhesives don’t work below 5°C. Spray foam expands unpredictably in cold temperatures. And working in a freezing metal box is miserable.

If you must work in winter, bring a space heater to warm the van first, or work during the warmest part of the day.

Q: How long does van insulation take to install?

For a DIY job:

• Acoustic deadening: 1 day
• Main insulation (walls, floor, roof): 3-5 days
• Finishing (sealing, vapour barrier): 1-2 days

Budget a week of solid work for a thorough job. Rush it, and you’ll miss gaps and thermal bridges that haunt you later.

Q: Will insulation stop my van heating up in summer?

It helps, but British summers are rarely that extreme. The bigger factor is ventilation — roof vents, window position, parking in shade.

Insulation slows heat transfer both ways, so it does reduce how fast your van heats up in sun. But once it’s hot, you need ventilation to cool it down.

Where to Buy (UK Sources)

Celotex/Kingspan PIR Boards:

• Wickes (trade counter, best prices)
• Selco (trade account helpful but not essential)
• Travis Perkins
• Screwfix (limited selection)

Armaflex & Flexible Foam:

• Amazon UK (good selection, quick delivery)
• Toolstation
• Screwfix

Acoustic Deadening:

• Amazon UK – Dodo Mat (best prices)
• eBay (watch for sales)

Sheep’s Wool:

• The Natural Building Store
• Ecological Building Systems
• Amazon UK (limited selection)

Expanding Foam, Tape, Adhesives:

• Screwfix (cheapest)
• Toolstation
• Amazon UK (convenience)

Pro tip: Buy PIR boards from trade counters early morning or late afternoon — you’ll get offcuts and damaged sheets cheap. I’ve saved £100+ doing this. Cosmetic damage doesn’t matter when it’s hidden behind walls.

My Final Thoughts

Insulation isn’t sexy. It’s not going to get you Instagram likes. But it’s the single most important decision you’ll make in a van conversion.

Spend money here. Do it properly. And I promise you’ll be comfortable in your van for years to come.

Skimp on insulation, and you’ll spend every cold night regretting it. I know, because I did exactly that in van number one. The £600 I thought I saved cost me in misery, condensation, and eventually ripping it all out to start again.

My current van? It’s properly insulated. I’ve slept in Scottish winters. Welsh rainstorms. That weird humid heat we get in July. And it’s always been comfortable.

That’s not luck. That’s decent insulation, properly installed, with attention paid to the boring details everyone skips.

Do it right the first time. Your future self will thank you.

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Affiliate Disclosure: This article contains Amazon affiliate links. If you purchase through these links, I may earn a small commission at no extra cost to you. This helps keep TheFeralWay running and allows me to keep testing gear and building vans. I only recommend products I’ve genuinely used or thoroughly researched.