The three jobs of van insulation
- Slow heat flow through the metal skin (measured as R-value or thermal conductivity).
- Control condensation, which forms when warm, humid air hits cold metal.
- Reduce noise – a welcome side effect of most materials.
Materials compared
| Material | Insulating value | Moisture behaviour | Notes |
|---|---|---|---|
| Sheep wool | Good | Absorbs and releases moisture without losing much performance | Easy to stuff into cavities; check for treatment against moths |
| Closed-cell foam boards (XPS, PIR) | Very good per thickness | Doesn't absorb water | Must be cut to fit tightly; gaps behind boards can trap condensation |
| Spray foam (closed-cell) | Very good | Seals and bonds to metal | Professional application recommended; difficult to remove later |
| Polyester / recycled PET wadding | Good | Doesn't hold water | Easy, itch-free, good for cavities |
| Foil bubble products | Limited unless facing an air gap | Can act as a barrier | Best as a radiant layer, not primary insulation |
The exact R-values depend on product and thickness – compare manufacturer data sheets for the specific product you're buying.
Practical rules
- Treat bare metal first: rust-proof any scratches and cut edges.
- No gaps: heat and moisture find the weakest point.
- Insulate the floor – often forgotten and a major cold source.
- Windows lose the most heat; insulated covers make a big difference overnight.
- Ventilate: insulation reduces condensation but a roof fan removes moisture.
Fire safety
Check the fire rating of every material, particularly near a diesel heater and electrical components. Keep clearance distances specified by appliance manufacturers.
Frequently asked questions
What is the best insulation for a camper van?
There's no single best. Many builders combine closed-cell foam boards on flat panels with a moisture-tolerant fill such as sheep wool or polyester in cavities. The key is avoiding gaps and managing condensation.
Do I need a vapour barrier in a van?
Opinions differ. Metal vans have many unsealable gaps, so a perfect vapour barrier is hard to achieve. Many builders prefer materials that tolerate moisture plus good ventilation. If you use a barrier, make it continuous.
Is reflective foil insulation worth it?
Foil only reflects radiant heat when facing an air gap. Glued directly against metal with no gap it adds little insulation – it's often used as a radiant layer, not the main insulation.
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