How much insulation does a campervan need? Square metres, boards and kilograms, per van
· 8 min read
A high-roof, long-wheelbase van has about 31 m² of steel to insulate: roughly 7 m² of floor, 17 m² of walls and rear doors, and 7 m² of ceiling. With 12 % cutting waste that is 35 m² of board — 47 XPS boards of 1250 × 600 mm, or 13 PIR sheets of 2400 × 1200. A mid-size van is closer to 20 m². Everything else in an insulation plan — material, thickness, weight, cost — is arithmetic on those areas, and the areas come from the van, not from a rule of thumb.
This guide computes them for eight common bases. If your van is not in the table, the insulation calculator has all 159 variants and takes a typed L × W × H too.
Where the square metres come from
Three surfaces, one box. The interior cargo area is a length, a width between the walls and a height from floor to headliner:
- Floor = length × width. Flat, easy, board territory.
- Walls = two sides of length × height, plus the rear-door aperture (the doors get insulated like a wall). Ribbed and curved — the surface that decides your material.
- Ceiling = length × width again. The biggest temperature difference in the van sits here, so it is the surface to spend on.
The numbers below are the bare shell: windows, roof fans and doors are not subtracted, and neither are the ribs that hold nothing. That is the right number for a shopping list — you buy for the panel and cut around the hole. It is not the number for a heat-loss calculation, which is why the planner subtracts openings (more on that at the end).
Shell area per van, and what it buys
Computed from each van's published interior dimensions. Boards assume 25 mm on every surface with 12 % waste: XPS in the common 1250 × 600 format, PIR in 2400 × 1200 sheets.
| Van | Floor | Walls + doors | Ceiling | Total | XPS boards | PIR sheets |
|---|---|---|---|---|---|---|
| Volkswagen Transporter L2H1 | 4.8 m² | 9.9 m² | 4.8 m² | 19.6 m² | 31 | 8 |
| Ford Transit Custom L2H1 | 5.2 m² | 10.1 m² | 5.2 m² | 20.5 m² | 32 | 10 |
| Fiat Ducato L2H2 | 5.8 m² | 14.9 m² | 5.8 m² | 26.6 m² | 41 | 12 |
| Mercedes-Benz Sprinter L2H2 | 5.8 m² | 16.3 m² | 5.8 m² | 28.0 m² | 43 | 13 |
| Ford Transit L3H2 | 6.2 m² | 15.8 m² | 6.2 m² | 28.2 m² | 44 | 13 |
| Fiat Ducato L3H2 | 6.9 m² | 17.1 m² | 6.9 m² | 31.0 m² | 48 | 13 |
| Volkswagen Crafter L3H3 | 6.3 m² | 16.3 m² | 6.3 m² | 28.9 m² | 45 | 13 |
| Fiat Ducato L4H2 | 7.6 m² | 18.6 m² | 7.6 m² | 33.8 m² | 52 | 14 |
Two things stand out. The walls are more than half of every van — so the material that fits the walls (curves, ribs, sliding-door pocket) matters more than the material that fits the floor. And the step from a Transporter to a Ducato L3 is not 30 % more van, it is 60 % more steel, because height enters the wall area twice.
The materials, in the units that matter
Insulating power is thickness ÷ λ (thermal conductivity). Forums quote R per inch; datasheets quote λ in W/mK. Both, side by side, with the planning figures the calculator uses:
| Material | λ (W/mK) | R per inch | Density | Waste | Format |
|---|---|---|---|---|---|
| PIR / polyiso board | 0.022 | 6.5 | 31 kg/m³ | 12 % | 2400 × 1200 sheet |
| XPS board | 0.033 | 4.4 | 33 kg/m³ | 12 % | 1250 × 600 board |
| Sheep wool | 0.038 | 3.8 | 18 kg/m³ | 5 % | 5 m² roll |
| Thinsulate SM600L | 0.042 | 3.4 | 12 kg/m³ | 8 % | 1.52 m roll, by the metre |
| Reflectix foil bubble | ~0.144 | ~1 | 30 kg/m³ | 5 % | 1.22 × 15.2 m roll |
Read the R-per-inch column as warmth per centimetre of lost living space. PIR buys the most, which is why it is the floor default: the floor is flat and every millimetre there is headroom. On the walls the ranking bends — boards do not follow a Sprinter's curve or fill the ribs, so most builds put wool or Thinsulate in the cavities and a thin continuous foam layer over the top. The space-cost guide does the centimetres side of that trade.
What it weighs and what it costs
Less than people fear. 25 mm of XPS over the Ducato's 31 m² is about 26 kg; 25 mm of PIR about 24 kg; 50 mm of sheep wool about 28 kg. The plywood lining that goes on top weighs more than the insulation under it — 5.5 mm ply over the same walls and ceiling is around 90 kg. Both go into the payload, and both are in the planner's weight model once you set them.
Cost at EU street prices (checked Aug 2026), linear in thickness: XPS about €3 per m² and 10 mm, PIR €2.80, wool €2.20, Thinsulate €4. For the Ducato that is roughly €260 of XPS at 25 mm across the shell, before adhesive, tape and the lining. Your timber yard's quote wins over this; the calculator is there to make the quote checkable.
Reflectix, honestly
Foil bubble wrap is a radiant barrier: it reflects heat across a still air gap. The R-values on the packaging are measured with such a gap on both sides. Glued to a van wall there is no gap, and the product is worth about R-1 per inch — the 8 mm you actually get is R-0.3. It has a use as a vapour-tight inner face over real insulation; on its own it is a very expensive way to keep a van cold. The calculator lets you pick it, and tells you this every time you do.
What the calculator cannot know — and the planner does
The public tool works from the shell box. It does not know where your windows are, how big the roof fan cut-out is, or that you removed the rear doors' lower panels. The VanPlot editor does: its Shell build-up reads every opening you have drawn and subtracts it, then writes the insulation weight into your payload and the material rows into the Build Sheet. It also shrinks the interior by the thickness you chose, so you see whether the bed still fits across before anything is glued. Start with the calculator, then take the plan into the editor with your real van.
