Choosing between cork and Armaflex for van insulation comes down to what you want the material to do: Armaflex insulates better at the same thickness and acts as its own vapour barrier, while cork is a natural material that lets water vapour through. Armaflex is rated at 0.033 W/m·K against 0.039 to 0.040 for expanded cork, and the two carry different fire ratings. This comparison sets out the datasheet figures, the condensation question and the cost per square metre.
1. Armaflex: 0.033 W/m·K, built-in vapour barrier, self-adhesive in its van version, fire rating B-s3,d0.
2. Expanded cork: 0.039 to 0.040 W/m·K, vapour-permeable, natural material, Class E for fire.
3. Sprayed cork: a coating a few millimetres thick, best paired with a thicker insulation layer behind the lining.
Van insulation compared on the datasheets
For van insulation, thermal conductivity, written λ (lambda), measures how easily heat passes through a material. The lower it is, the better the material insulates at a given thickness. For Armaflex, the UK listing for AF/Armaflex published by Armacell UK on NBS Source gives 0.033 W/m·K at 0 °C, a water vapour resistance factor μ of 10,000 or more, a B-s3,d0 fire rating and a working range from −50 °C to +110 °C.
For cork, the technical datasheet for Amorim’s expanded cork board (in French) gives 0.039 W/m·K, or 0.040 under the French ACERMI certification. It lists water vapour transmission as MU20 measured on 60 mm, a Class E reaction to fire and a density of 110 kg/m³, give or take 10. French retailer h2r-equipements also lists 0.039 W/m·K for its SOLIEGE sprayed cork.
| Criterion | AF/Armaflex | Amorim expanded cork |
|---|---|---|
| Conductivity λ | 0.033 W/m·K | 0.039 W/m·K (0.040 ACERMI) |
| Vapour resistance μ | 10,000 or more | 20 (MU20 on 60 mm) |
| Reaction to fire | B-s3,d0 | Class E |
| Material | Elastomeric foam | Natural expanded cork |
The gap in λ looks small, yet it translates straight into thickness. To match the thermal resistance of a 0.033 material, a 0.039 material needs to be roughly 18 % thicker, a simple sum from the two figures.
How thickness changes thermal resistance for van insulation
Thermal resistance, R, is the thickness in metres divided by the conductivity. Amorim publishes its own values: R = 0.25 m²·K/W for 10 mm of expanded cork and 0.75 for 30 mm. Applying the same formula to Armaflex, 19 mm gives 0.019 divided by 0.033, or about 0.58 m²·K/W.
| Material and thickness | Calculation | Resistance R |
|---|---|---|
| Expanded cork 10 mm | Amorim figure | 0.25 m²·K/W |
| Armaflex 19 mm | 0.019 ÷ 0.033 | 0.58 m²·K/W |
| Expanded cork 30 mm | Amorim figure | 0.75 m²·K/W |
| Sprayed cork 3 mm | 0.003 ÷ 0.039 | 0.08 m²·K/W |
The table makes each product’s role clear. A few millimetres of sprayed cork add very little thermal resistance on their own; their value lies in covering the bare metal continuously and dealing with condensation. Effective van insulation needs thickness, whether in Armaflex or in cork boards.
On thickness, h2r-equipements’ buying guide names 19 mm Armaflex “Chezmoi” as the most widely used in vans. It also lists 10 mm and 16 mm for lighter insulation, 25 or 32 mm to fill recesses, and 6 mm for joints. The choice mostly comes down to how much living space you are willing to give up, something worth weighing as early as choosing the vehicle, as our guide on choosing a van to convert explains.
Condensation and vapour barriers for van insulation
Water vapour is where cork and Armaflex differ most. With a μ of 10,000 or more, Armaflex blocks vapour: h2r-equipements sells it as insulation with a built-in vapour barrier and advises covering all the bare metal without gaps to break thermal bridges, claiming that condensation will then be neutralised. That is the retailer’s claim, and it cites no test.
Cork takes the opposite approach. Amorim lists its vapour permeability among its advantages, and h2r describes the board as water-repellent and rot-proof, with no risk of mould from damp. Sprayed cork, for its part, is sold as a way to reduce condensation inside the van.
FarOutRide, a build guide many converters follow, takes a stance close to cork’s in its guide to van insulation. Its authors explain that a vapour barrier exists to stop moist air from inside the van reaching cold surfaces, but believe that moist air will inevitably come into contact with the cold structure of a van anyway. Their approach is to let the insulation layers breathe, with no vapour barrier. They do insist on thermal bridges, the paths heat takes by conduction through the metal, and add a thermal break between exposed metal and the cabinets.
That point holds whichever van insulation you choose. Bare metal left behind a cabinet, an uncovered cross member or a screw running through the insulation each create a path for heat and a cold spot where moisture can settle. Plan the thermal breaks at the same time as the insulation itself, before any lining goes up, because they are far harder to add once the furniture is in place.
Fitting van insulation: adhesive, preparation and limits
Fitting van insulation starts with adhesive: the Armaflex sold for vans is self-adhesive, rated to a maximum surface temperature of 85 °C according to h2r, a limit worth checking on a dark roof in full sun. For joints, the datasheet for Armaflex 520 adhesive describes a polychloroprene glue applied in a thin film, ideally at 20 °C, with 36 hours to cure, and classed as highly flammable: keep the van well ventilated while you glue.
Sprayed cork takes more preparation: keying painted surfaces, degreasing with acetone, spraying with a compressor at 4 bar, leaving at least 24 hours between coats, for a coverage of roughly 1.5 to 2 kg/m² depending on the retailer’s page. For this kind of van insulation, expanded cork boards are rigid panels, sold at 1,000 × 500 mm by h2r, cut to shape before gluing to the metal: plan the layout panel by panel beforehand to keep offcuts to a minimum.
Cost per square metre at one retailer
Prices below were taken from the h2r-equipements website on 1 October 2026, for comparing orders of magnitude only.
| Product | Listed price | Price per m² (calculated) |
|---|---|---|
| Armaflex Chezmoi 19 mm, 6 m² roll | €98.00 incl. VAT | €16.33/m² |
| SOLIEGE sprayed cork, 6 kg bag for 8 m² | €140.00 incl. VAT | €17.50/m² |
| Amorim expanded cork board, 1,000 × 500 mm | from €117.55 incl. VAT (60 mm) | depends on thickness |
For the same area, 19 mm Armaflex and sprayed cork land in the same price bracket, while their thermal resistance is in a different league. Sprayed cork earns its place as a finishing and moisture-management layer, combined with thicker insulation.
Cork or Armaflex for your kind of travel
| Profile | What to aim for |
|---|---|
| Weekends and summer trips | 10 to 19 mm Armaflex fitted without gaps, or sprayed cork if damp worries you more than cold |
| Regular travel in all seasons | 19 mm Armaflex, 25 or 32 mm in recesses, thermal breaks between metal and cabinets |
| Full-time living and winter | Thickness comes first: compare R values, then choose between a built-in vapour barrier and breathable materials according to how you see condensation |
Before settling your van insulation, decide how you want to handle moisture, since that is what really separates the two materials. Then work out the thermal resistance of each option at the thickness your van can spare, and check the fire rating on the datasheet of the exact product you buy.