What is condensation?
The dangerous choice when “experts” talk freely
Insulating your campervan can feel like navigating a jungle of opinions and advice. It’s easy to get overwhelmed when everyone insists their method is the only right way. Even my friends and I, who are construction engineers, sometimes scratch our heads over this subject. Thatäs why we diceded to write a campervan insulation guide, filled with our experiens and knowledge. But notice, always check for local rules and law where you live.
It’s important to remember that we’re primarily talking about insulating a metal van shell, not a timber-framed house. The rules are similar, but not identical.
Here’s the good news: you get to choose the solution that works for you and we’ll do our best to guide you.
Instead of seeing all the different recommendations as a barrier, you can look at them as opportunities to explore and find the ideal setup for your tiny home on wheels. We’ve tried to summarise the most common approaches we’ve come across, which has resulted in three main categories. Each has its pros and cons – but if you understand them and install things correctly, you can relax.
Do your own research, then make your own informed decision.
We’re going to jump straight into one of the most talked-about issues among people converting vans to campervans: condensation.
A bit later, we’ll take a closer look at the three main insulation methods, so you can feel confident in your choice and hopefully have a bit of fun along the way.
So let’s break it down
Condensation is the process where water vapour in the air turns into liquid when it cools down. This happens when warm, moist air comes into contact with a cold surface, causing water in the air to form tiny droplets on that surface.
Think of an ice-cold drink on a hot summer’s day, the cold glass pulls moisture from the air and beads of water form on the outside. The same thing can happen inside your converted van.
Why does condensation form in a converted van?
In a campervan, several factors can lead to condensation:
- Heating and cooling cycles:
When you’re driving in cold weather and then switch off the engine, the temperature inside the van can drop quickly. If you then get into the van with damp clothing, or start cooking, the warm, moist air can condense on cold surfaces such as the walls and ceiling. - Wet clothes and gear:
When you bring in wet clothes or outdoor gear, you increase the humidity inside the van, which raises the risk of condensation. - Breathing:
Even a small amount of breathing from the people inside produces moisture. In a small, enclosed space with poor ventilation, water vapour can build up surprisingly quickly. - Poor ventilation:
If your van doesn’t have a good ventilation system, moisture-laden air can’t escape, which leads to condensation.
How do you tackle condensation?
Ventilation in a campervan
- Install a roof vent or fan to ensure moist air can escape and fresh air can enter.
- Open windows or doors during the day, especially after cooking or when there’s been a lot of activity inside the van.
Dehumidifier
- Use a dehumidifier to pull excess moisture out of the air. There are compact, portable units that work well in campervans.
Dry storage
- Avoid storing wet clothes or gear inside the van. Let them dry outside or in a well-ventilated area before bringing them in.
Use moisture-absorbing products
- Place moisture absorbers, such as silica gel packs or dedicated dehumidifier tubs, inside the van to help lower humidity levels.
Insulate a campervan
- Use suitable insulation materials and methods (we’ll come back to this) and combine them with good ventilation.
Regular checks
- Regularly inspect hidden areas, corners and behind panels for signs of moisture, mould or damp spots so you can act early.
One of the most exciting (and sometimes frustrating) parts of building your own campervan is trying to make everything fit into such a limited space – it’s like solving a giant 3D puzzle. Stay flexible and remember that your “must-haves” and “nice-to-haves” will probably change over time, especially once you actually start living in the van.
If you can, take the van on test trips during the build. This helps you quickly spot what works, what doesn’t, and what needs improving before you go any further.
Why can condensation become a problem?
What are the risks of condensation, and what can it cause over time? These are the most common consequences:
- Mould and damp:
If condensation isn’t dried off, it can lead to mould and fungal growth, which can cause health problems and musty smells. Mould can be difficult to remove and can damage materials. - Material damage:
Condensation can damage timber, insulation and other building materials in your van. If these materials become saturated, they can lose strength and shorten the lifespan of your interior. - Poor air quality:
Increased humidity can lead to poorer air quality and unpleasant odours inside, which affects your comfort and overall experience of living in the van.
Use natural light and “free” heating/cooling
Installing advanced heating systems or air-conditioning can be expensive, but there are simpler and more cost-effective ways to keep your campervan comfortable:
Keep your campervan cooler
- Park in the shade and open windows for cross-ventilation.
- Use USB-powered, solar-charged fans to circulate air.
- Install a roof vent, and if you’re on a budget, you can fix a computer fan into the vent hatch for simple, low-cost active ventilation.
Keep your campervan warmer
- Park in sunny spots in winter for free solar gain.
- Use dark curtains or blankets at night to help retain heat.
- Add cheap reflective insulation (like foil-backed bubble wrap) in the windows. Tip: tension it in place or use suction cups to hold it.
These small, simple solutions can save you a lot of money and make vanlife far more comfortable.
Use natural light and “free” heating/cooling
Installing advanced heating systems or air-conditioning can be expensive, but there are simpler and more cost-effective ways to keep your campervan comfortable:
Keep your campervan cooler
- Park in the shade and open windows for cross-ventilation.
- Use USB-powered, solar-charged fans to circulate air.
- Install a roof vent, and if you’re on a budget, you can fix a computer fan into the vent hatch for simple, low-cost active ventilation.
Keep your campervan warmer
- Park in sunny spots in winter for free solar gain.
- Use dark curtains or blankets at night to help retain heat.
- Add cheap reflective insulation (like foil-backed bubble wrap) in the windows. Tip: tension it in place or use suction cups to hold it.
These small, simple solutions can save you a lot of money and make vanlife far more comfortable.
Summary
Insulating your campervan doesn’t have to be difficult, but it is important that you understand the purpose and the basics. If you want a healthy, comfortable indoor climate, you need to use the right materials in the right places.
Condensation can be a quiet but serious enemy in your converted van. By understanding how and why it forms, you can take steps to prevent it and protect your investment.
With the right combination of ventilation, insulation and dehumidification, you can enjoy a comfortable indoor environment in your campervan, whatever the weather. Make sure you have a clear plan for controlling moisture, your campervan will thank you for it.
Top 3 types of insulation material
1. Loose – Fill insulation
- Wool: A natural material that’s both sustainable and effective. Wool is not only environmentally friendly; it’s also excellent at holding heat, which makes it ideal for cold winter adventures. On top of that, wool can absorb moisture without feeling wet.
- Fibreglass wool: One of the most popular insulation options on the market. It’s relatively cheap and widely available – but be careful, it can be irritating to handle. Always wear gloves and a mask so you don’t end up itchy!
- Rock wool (stone wool): A slightly heavier but very effective solution. It’s fire-resistant and provides good sound insulation, which can be a blessing when you want peace and quiet in your van.
2. The Board Method – Structured, stable and beginner-friendly
If you prefer a more controlled and easy-to-install approach to insulating your campervan, the board method is a fantastic option. This method uses rigid insulation boards that you cut to size and fit into your van’s walls, roof and floor. It’s a popular choice among DIY van converters who want predictable results with minimal mess.
XPS (Extruded Polystyrene) Boards
XPS is one of the most widely used materials in campervan conversions thanks to its excellent thermal resistance, high compression strength and low water absorption.
It’s lightweight, easy to cut, and provides a reliable insulation layer for both floors and walls.
Benefits of XPS insulation:
- Affordable and easy to find in most DIY stores
- Fantastic thermal insulation for maintaining a warm campervan in winter
- Moisture-resistant, making it ideal for cold and damp climates
- Works perfectly under the subfloor due to its strength
Drawbacks:
- Needs to be sealed properly to avoid air gaps
- Not bendable – not ideal for curved van walls
PIR (Polyisocyanurate) and PUR Boards
PIR and PUR insulation boards are extremely efficient and commonly found in professional building insulation. They offer some of the highest R-values per cm of thickness, which is perfect if you want to maximise headroom in your van.
Why PIR/PUR works well in campervans:
- Excellent insulation performance with minimal thickness
- Comes with foil-faced surfaces for improved radiant heat reflection
- Lightweight but firm, easy to glue in place
Keep in mind:
- Not flexible, so installation requires precise cutting
- More expensive than XPS
3. The Foam Method – Sealing gaps for maximum performance
If you’re looking for a highly efficient, air-tight insulation method that tackles everything from thermal bridging to soundproofing, the foam method is one of the best options. This includes materials like spray foam insulation, closed-cell foam sheets, and self-adhesive foam rolls commonly used in professional van conversions.
Closed-cell foam (Armaflex, Kaiflex, Celotex)
Closed cell foam has become one of the most popular campervan insulation products in Europe, especially brands like Armaflex and Kaiflex. These materials combine excellent thermal resistance with moisture control.
Why closed-cell foam is ideal for van conversions:
- Acts as both insulation and a built-in vapour barrier
- Flexible and perfect for curved van walls and ribs
- Extremely moisture-resistant – prevents condensation build-up
- Great for soundproofing and vibration reduction
- Easy to install with self-adhesive backing
This makes it one of the most “all-in-one” solutions on the market.
Natural Fibre Boards
For van builders looking for an eco-friendly insulation option, natural fibre boards like cork, wood fibre and hemp offer a sustainable and breathable alternative. They provide solid thermal performance, help manage moisture and naturally absorb sound, creating a healthier and more comfortable campervan interior.
Benefits of Fibre Boards:
- Breathable – helps reduce the risk of trapped condensation
- Sustainable and non-toxic
- Provides both thermal insulation and sound dampening
Keep in mind:
- Not as moisture-resistant as XPS
- Can be harder to find in standard sizes for vans
How to install board insulation in a campervan
- Measure, cut and fit boards tightly into each cavity
- Use a strong adhesive or double-sided tape to secure boards to metal panels
- Seal edges with aluminium tape or expanding foam to eliminate air gaps
- Combine with sound-deadening mats for quieter driving
- Add a reflective vapour-control layer if needed
The board method is ideal for beginners because it offers structure, stability and predictability – and it’s especially popular for DIY campervan floors.
The Foam Method – Sealing gaps for maximum performance
If you’re looking for a highly efficient, air-tight insulation method that tackles everything from thermal bridging to soundproofing, the foam method is one of the best options. This includes materials like spray foam insulation, closed-cell foam sheets, and self-adhesive foam rolls commonly used in professional van conversions.
Closed cell foam (Armaflex, Kaiflex, Celotex foam etc)
Closed-cell foam has become one of the most popular campervan insulation products in Europe – especially brands like Armaflex and Kaiflex. These materials combine excellent thermal resistance with moisture control.If you’re looking for a highly efficient, air-tight insulation method that tackles everything from thermal bridging to soundproofing, the foam method is one of the best options. This includes materials like spray foam insulation, closed-cell foam sheets, and self-adhesive foam rolls commonly used in professional van conversions.
Why closed-cell foam is ideal for van conversions:
- Acts as both insulation and a built-in vapour barrier
- Flexible and perfect for curved van walls and ribs
- Extremely moisture-resistant – prevents condensation build-up
- Great for soundproofing and vibration reduction
- Easy to install with self-adhesive backing
This makes it one of the most “all-in-one” solutions on the market.
Spray Foam Insulation (PU Foam)
Spray foam insulation is a more advanced option, but when applied correctly, it offers unbeatable coverage and eliminates virtually all air gaps. It expands into every corner, making it perfect for older vans with uneven metalwork.
Foam Carpet Underlay and Rubber Foam
These lightweight foams work brilliantly as a complementary layer to other insulation types. They help reduce road noise, absorb vibrations, and provide a soft base layer for interior cladding.
Perfect for:
- Under flooring
- Inside door panels
- Wheel arches
- Behind furniture
Benefits:
But consider:
Installation method
Först och främst, se till att skydda fönster och dörrar för att förhindra att damm och skräp flyger in under installationen. Fyll sedan utrymmena mellan väggarna, taket och golvet med det valda materialet. När du använder ull eller stenfiberull, glöm inte att fuktskydda dem med en ångspärr och se till att led bort ev. kondesbildning från plåten.
Each material and method has its own pros and cons – in terms of cost, ease of installation, sound insulation, fire safety and moisture handling. The important thing is to understand how they behave so you can choose what fits your priorities best.
How we recommended to insulating your campervan
Here’s a suggested step-by-step sequence for insulating a van:
1. Planning before you start the conversion
- Before you touch any insulation, plan how you want the van to look and which areas need insulation.
- Strip everything out of the cargo area, including floor coverings and any existing lining, so you have a clean workspace.
- Check all nooks, cavities and screw holes. Apply rust protection and a coat of paint where needed to avoid headaches later.
- Clean and degrease all surfaces.
- Install sound-absorbing and damping materials to minimise unwanted noise while driving.
2. Roof
- Start with the roof; it’s the most exposed surface for temperature changes and the hardest to reach once everything else is installed.
- Use suitable insulation (for example spray foam, board insulation or bonnet insulation products from brands like Biltema).
- Consider adding a reflective layer to block radiant heat and reduce noise from above.
- Decide whether you need a vapour control layer, depending on your chosen materials and climate.
3. Walls
- Next, move on to the walls. If you’re using a loose-fill method, make sure you fill all gaps and cavities thoroughly.
- Polyester fibre or spray foam can be used where there’s a high risk of condensation and direct contact with metal. (Note: some channels should be kept open for drainage and ventilation.)
- A board-based approach can also be used to create a stable and effective insulation layer.
4. Floor
- After the walls, you can move on to the floor. Here it’s important to choose materials that can handle both moisture and wear.
- Use XPS boards or another suitable material for floor insulation. Consider adding a moisture barrier to protect against mould.
5. Window and door areas
- Insulate around windows and doors. Flexible materials work well here as they can follow complex shapes and tight spaces.
- Use sealants or weatherstripping to prevent draughts and improve energy efficiency.
6. Ventilation
- Don’t forget about ventilation. Good airflow is crucial to preventing condensation and mould, especially in damp climates.
- If you don’t have a roof vent or fan, consider fitting wind deflectors on the cab windows so you can crack them open even in rain. This can do wonders on a hot or humid summer’s night – for both you and the van.
7. Interior lining and furniture
- Once the insulation is in place, you can move on to interior finishes and furniture.
- Decide what type of wall and ceiling lining you want.
- Plan how much visible and hidden storage you need and where it should go.
8. Test and adjust
- Finally, test your insulation to make sure it works as expected.
- Check for cold spots, draughts or damp areas and make adjustments where needed.
Our insulation strategy
When theory meets reality, compromises are inevitable. The perfect material doesn’t exist, but these are the key factors we think you should weigh up:
- Ease of installation for beginners
- Risk of damaging the van (e.g. warped panels)
- Condensation and moisture control
- Ability to follow curved and uneven surfaces
- Material properties (e.g. maximum temperature and compressive strength)
With this in mind, we chose the following strategy for our own campervan:
1. Floor insulation: XPS boards
For the floor, we chose XPS boards because they provide a stable base and good thermal performance. We started by levelling out uneven areas with 1 cm boards, then added another 2 cm to achieve a decent insulation thickness.
After that, we laid plywood on top and finished with a vinyl floor for a durable, easy-to-clean surface.
2. Walls and roof: thermal foil and foam
For the walls and roof, we used a combination of thermal foil and foam. Thermal foil is easy to install and works well for both sound and heat insulation. With spray adhesive or contact adhesive you can fix it neatly to the panels.
3. Fönster: Anpassade isoleringsskydd
För att minimera värmeförlusten på vintern använde vi oss av fönsterskydd gjorda av Thermofolie och tyg. Dessa gör en stor skillnad vid kalla temperaturer och är nästan ett måste under vintern. Finns även att köpa färdigsydda från Amazon och Biltema mm.
Windows in a DIY campervan: Custom insulation covers
To minimise heat loss in winter, we made window covers out of thermal foil and fabric. These make a big difference in cold conditions and are almost a must in winter. You can also buy ready-made covers from Amazon, Biltema and similar retailers.
Final thoughts
You now have all the information you need to get started with insulating your campervan. Remember: it’s a process, and it’s completely fine to learn as you go.
Whether you’re aiming for a cosy winter cabin on wheels or a cool summer hideaway, a well-insulated van is the key to your dream home on wheels.
So grab your tools, trust your growing knowledge – and enjoy this amazing project. You’re on your way to new adventures, and with your freshly insulated campervan you’ll be ready for whatever comes next.