Camper van insulation: materials, R-value and tips
Good insulation is essential for a comfortable camper van. It keeps warmth inside in winter and outside in summer, and prevents condensation problems. In this guide we discuss the most popular insulation materials, how to choose the right thickness and what to watch out for.
Calculate your insulation material
Why insulation is so important
An uninsulated van is essentially a metal box. In winter it cools down extremely fast, in summer it becomes an oven. Without insulation:
• You lose up to 10× more heat than in an insulated van
• Moisture from the air condenses on the cold metal walls
• Water in pipes freezes in winter
• It becomes uncomfortable above 25°C outside temperature
Condensation is the biggest danger: moisture creeps between insulation and bodywork causing rust. This is invisible until it's too late. Good insulation with a vapor barrier prevents this.
Popular insulation materials compared
The four most commonly used materials for camper van insulation:
Armaflex (or similar closed-cell rubber): by far the most popular. Easy to work with, vapor-resistant, flexible. Thermal conductivity (λ): 0.033–0.038 W/mK (19 mm = R 0.53). Price: €15-€25 per m².
XPS (extruded polystyrene, e.g. Jackodur): rigid boards, high compressive strength, moisture resistant. Ideal for floors. Thermal conductivity (λ): 0.029–0.036 W/mK (30 mm = R 0.86). Price: €5-€10 per m².
Rock wool/glass wool: cheap with good insulation value, but absorbs moisture. Only use with proper vapor barrier. Thermal conductivity (λ): 0.032–0.040 W/mK (50 mm = R 1.38). Price: €3-€7 per m².
Reflective foil (e.g. Dodo): thin foil with reflective layer. Limited insulation value as sole layer, but good as supplement. Thermal conductivity (λ): >0.040 W/mK, works mainly by reflecting radiant heat.
PIR (polyisocyanurate, e.g. Recticel or Kingspan): rigid board with the best insulation value per centimetre. Lambda around 0.022 W/mK, so 30 mm already gives R 1.36 where Armaflex needs 49 mm for the same. Ideal on flat surfaces where interior space is precious. Downside: it is rigid, so awkward around curves and wheel arches, and you have to seal the joints carefully because the board itself is vapour-tight but the gaps between boards are not.
What thickness do you need?
The required insulation thickness depends on your climate and travel pattern:
Summer only in Southern Europe: 10-15 mm Armaflex is sufficient. It's mainly about blocking heat and preventing condensation.
Three-season in Western Europe: 19-25 mm Armaflex or equivalent. This is the sweet spot for most camper vans.
Four-season including winter: 25-40 mm total insulation thickness. Combine materials: XPS on the floor (20-30 mm), Armaflex on walls and ceiling (19-25 mm).
Keep in mind the loss of interior space. With 25 mm insulation on all sides, you lose about 5 cm in width and 2.5 cm in height. Measure this beforehand!
The 5 biggest insulation mistakes
1. No vapor barrier: moisture from the air condenses on the cold metal behind the insulation. Use closed-cell material (Armaflex) or apply a vapor barrier.
2. Forgetting thermal bridges: everywhere metal runs from outside to inside (screws, ribs, window frames) you lose heat. Insulate these points too.
3. Skipping wheel arches: wheel arches are a huge surface area directly exposed to outside air. Insulate them carefully.
4. Not insulating the floor: you lose a lot of heat through the floor, especially when parked on asphalt. Use XPS boards of at least 20 mm.
5. Insufficient ventilation: insulation without ventilation leads to moisture problems. Install a roof vent fan and ventilation openings.
R-value and lambda: what the numbers mean
Insulation comes with two numbers, and it pays to know what they say.
The lambda value (λ) is a material property: how well the material conducts heat, in W/m·K. Lower is better. PIR sits around 0.022, XPS around 0.034, Armaflex around 0.036 and rock wool around 0.035.
The R-value is what you actually get: the thermal resistance of a layer, calculated as thickness in metres divided by the lambda value. Higher is better. So 30 mm of PIR gives 0.030 / 0.022 = R 1.36, while 30 mm of Armaflex gives 0.030 / 0.036 = R 0.83.
R-values of successive layers can be added. Stick 19 mm of Armaflex onto 30 mm of PIR and you are at R 1.36 + 0.53 = R 1.89. On top of that comes a small contribution from the air on either side of the wall, which the insulation calculator accounts for.
The main thing to remember: the benefit per extra centimetre falls away. Going from R 0.5 to R 1.5 nearly halves your heat loss; going from R 2.5 to R 3.5 gains you only a fraction. In a van, where every centimetre of interior space counts, the practical optimum therefore sits lower than in a house.
Vapour control and the order of your build-up
The real risk in camper insulation is not cold but moisture. Two people sleeping in a van for a night produce roughly half a litre of water vapour between them, and cooking and showering add to that. That vapour migrates to the coldest place it can find, which is the inside of your sheet metal.
The order from inside out is therefore: your interior finish, then the vapour control layer, then the insulation, then the bodywork. The vapour barrier belongs on the warm side, so on the inside of the insulation. Put it on the wrong side and it traps moisture inside the insulation instead.
With closed-cell materials such as Armaflex or PIR the material itself is already vapour-tight. The problem then moves to the joints: every gap vapour can slip through is a place where condensation forms, exactly where you cannot reach it. Seal joints with vapour-tight tape and finish the edges around ribs and profiles carefully.
And leave no air gap between insulation and sheet metal. Air circulating there carries moisture to the cold metal, which is precisely what you want to avoid. Bond closed-cell material over its full surface.
Sound deadening is not insulation
Butyl sound deadening and thermal insulation are often confused, but they do very different things.
Sound deadening damps vibration in the panels. Large flat panels resonate while driving and you hear that as a tinny drumming. A few strips of butyl in the middle of each panel remove most of it. Covering more than roughly a quarter of the surface adds little and only costs weight, and it weighs a serious amount: a sheet of butyl is heavy.
Insulation slows heat transfer. Butyl barely helps there, because the layer is thin and the material conducts heat perfectly well.
The practical order is therefore: rust treatment first, then some butyl on the large panels against drumming, then the insulation, then the vapour control and the finish. Anyone using butyl in the hope of insulating pays in weight without return.
Calculate your insulation material
Use our surface calculator to determine how much insulation material you need for your van.
Frequently asked questions
- What is the best insulation material for a camper van?
- Armaflex (closed-cell rubber) is the most popular because it is easy to work with, acts as a vapor barrier and has a good insulation value. For the floor, XPS (Jackodur) is a better choice due to its compressive strength.
- How much does it cost to insulate a camper van?
- Budget €300-€600 for an average van (L3H2) with 19mm Armaflex. XPS for the floor costs €50-€100 extra. Rock wool is cheaper (€100-€200) but requires additional vapor barrier.
- How do you prevent condensation in a camper van?
- Use closed-cell insulation material (Armaflex) glued directly to the metal without an air gap. Ensure good ventilation (roof vent fan!) and avoid open water vapor sources like a gas stove without extraction.
- What does the R-value actually mean?
- The R-value is the thermal resistance of a layer: thickness in metres divided by the material's lambda value. Higher is better. 30 mm of PIR at lambda 0.022 gives R 1.36; the same 30 mm of Armaflex at lambda 0.036 gives R 0.83. Layers can be added together. Our insulation calculator works this out for you, including the contribution of the air on either side.
- Is PIR better than Armaflex?
- Per centimetre it is: PIR insulates roughly one and a half times as well, so you reach the same R-value in less thickness. But PIR is a rigid board and therefore awkward on curves, wheel arches and the thousand irregular shapes in a van. Many builders combine the two: PIR on the flat areas of walls and roof, Armaflex in the corners, around ribs and on the wheel arches.
- Do I need sound deadening mat?
- If you want to damp the drumming while driving, yes, but do not expect insulation from it. Butyl mat damps vibration in the panels, nothing more. A few strips in the middle of the large panels do most of the work; covering more than roughly a quarter of the surface adds little and costs unnecessary weight.
- Can I insulate over the factory insulation?
- Better not. The fibre mats sometimes fitted inside the panels from the factory absorb moisture and hold it against the sheet metal. Take them out, check the metal underneath for rust and treat that first. It is also the moment to inspect everything you will not see again for years.