Van Conversion Guide

Base Build

Insulation

Insulation is one of the most debated topics in van conversions — and for good reason. It plays two key roles:

  1. Thermal Barrier – keeping you warmer in winter and cooler in summer.

  2. Condensation Control – stopping moisture from forming behind your walls, which can quietly damage your van over time.

There are plenty of strong opinions online, but the truth is: three main insulation options all get the job done thermally. The real differences are in cost, ease of install, and sustainability. This guide breaks down what you actually need to know.

Acoustic Insulation (Sound Deadening)

Additional Tools:
Drill + Drill bits
Impact driver + timber screws
or
Nailgun/Hammer (If using nails)
Jigsaw
Jigsaw blades

A woman in black shorts and a tank top working inside an empty, partially stripped van, with tools on the floor and construction materials around her.

Before thermal insulation, it’s worth doing some soundproofing. This small step makes a big difference in comfort.

Benefits:

  • Reduces rattles and road noise

  • Makes the van feel more “homely”

  • Improves sleep quality

How to Install:

  • Use butyl-based mats (Linked here)

  • Apply directly to large flat panels (walls, ceiling, sliding door, wheel arches)

  • Press down firmly so there are no air gaps and a solid connection has been made

Hot Tip: Covering more than 50% of each panel gives minimal extra benefit. Save your budget for other parts of the build by applying just 50% coverage of sheet metal.

Hot Tip: Sound deadening is particularly important on the ceiling to dull the thud of raindrops on your roof while you’re trying to sleep at night.

Thermal Insulation

Good thermal insulation helps regulate temperature and prevents condensation. Let’s look at the main materials DIY builders use:

Thermal Insulation Options

Material Positives Negatives Cost Best Used For
Flexible Closed-Cell Foam Easiest Install
View Foam Rolls 		Lightweight, moisture-resistant, peel-and-stick, great at stopping airflow to cold metal. Most expensive; thinner (10 mm typical) so less R-value per layer vs thick boards. High Small vans; curved/irregular shapes; walls & ceilings.
XPS Foam (Extruded Polystyrene) Best Value
Shop XPS Boards 		Cheap, excellent thermal performance (high R per thickness), easy to source in 25–50 mm boards. Rigid boards are fiddly around curves; takes more time to fit & seal perfectly. Medium Larger vans; flat panels & floors; areas where thickness is available.
Natural Sheep’s Wool Eco Choice
Buy Wool Insulation 		Sustainable, breathable; can absorb & release moisture (“breathes” with the van); easy to work with. Slightly less thermally efficient; must be installed thoughtfully to avoid damp spots. Fair Eco builds; walls & ceilings in any van.

All three materials are thermally effective. Choosing comes down to:

  • Do you want the easiest install? → Closed-cell foam.

  • Do you want the cheapest high-performance option? → XPS.

  • Do you want the eco-friendly, natural choice? → Sheep’s wool.

Installation Tips

  • Cut insulation to fit tightly — avoid gaps.

  • Cover every exposed patch of metal (these are condensation points).

  • Use adhesive suitable for your chosen material.

  • Seal joins with cloth/foil tape to stop airflow.

  • Pay attention to tricky areas: wheel arches, ribs, doors, and roof.

  • Insulate the floor too (XPS or foam boards under subfloor).

Recommended Products

Closed-cell foam rolls (eg. Car Builders or similar)

  • XPS insulation boards

  • 100% natural sheep’s wool insulation

  • Cloth tape

  • Butyl-based sound deadening mats

FAQ

  • Not always. In small vans with good ventilation and breathable insulation (like wool), a full vapor barrier may trap moisture behind the walls rather than help. Focus instead on sealing insulation properly and allowing airflow behind cladding where possible.

  • Yes, especially in colder climates. XPS or closed-cell foam boards work well here—just make sure they’re compressed evenly under your subfloor.

  • Use what fits your build. Around 10–25mm for walls/ceiling is common in small vans. You don’t need to max it out—tight, sealed coverage is more important.

  • These materials have their place, but they’re often overhyped. Alone, they don’t insulate much. Paired with proper materials (like foam or wool), they can reflect radiant heat—but don’t rely on them as your primary insulation.

Tips & Tricks

Use wood glue in the joins

Adding a bead of wood glue to each tongue-and-groove joint helps seal out moisture — ideal for areas above cooktops or beds.

Cut for lights as you go

It’s much easier to cut clean openings for lights or fans during installation than trying to drill through the ceiling later.

Match the ceiling curve

Measure at both ends of each board to accommodate any curve in the ceiling — this gives you tight, professional-looking edges.

Treat both sides of every board

Sealing the back side of your timber helps prevent warping and improves moisture protection — don’t skip it!