You're building a Sprinter van for off-grid life in Australia. You need insulation. But which one? Spray foam, wool, or PIR? We'll cut through the noise. No fluff. Just what works.
Van wall cross-section showing the five insulation layers from outer skin to interior cladding.
R-Values for Aussie Climates (Stop Wasting Money)
Forget the marketing. In Australia, you need:
Roof: R4.0 minimum (R5.0 if you're in QLD/NT or want to sleep without sweating)
Walls: R3.0 minimum (R4.0 if you're in Victoria/Tasmania)
Insulation Showdown: Spray Foam vs Wool vs PIR
Insulation
Pros
Cons
Cost (Installed)
Aussie Reality
SPRAY FOAM (Closed Cell)
Seals air leaks, high R-value, one-off install
Messy, expensive, needs pro
$15-$25/sqm
Only worth it if you're in the tropics and want it done fast. Don't DIY.
WOOL (Recycled)
Natural, breathable, handles humidity
Expensive, low R-value, needs protection
$10-$20/sqm
Only if you're in humid coastal areas and want "eco". Otherwise, waste of cash.
PIR (Polyisocyanurate)
High R-value, rigid, easy to install, cheapest
Needs sealing at edges, not "natural"
$8-$15/sqm
Best value. Get 75mm for roof (R3.75 ≈ R4.0). Done.
Key Aussie Truth: PIR gives you R3.75 at 75mm. Wool needs 100mm for R3.0. Spray foam? It's good but overkill for most Aussies. PIR is the only one that makes sense.
Practical Tips (No Fluff)
Don't skip the vapor barrier if using PIR or wool. Spray foam doesn't need it. Use Tyvek on the inside.
75mm PIR is non-negotiable for roof. 50mm is a joke. You'll fry in summer.
Wool? Wrap it in Tyvek. Otherwise, it gets soggy and smells like wet dog.
Insulate the floor. It's the same as walls but harder. Do it. Or you'll be freezing.
Get quotes from local suppliers. Don't trust online prices. They're usually wrong.
Australian Suppliers & Pricing (indicative prices)
Here's where to get it without getting ripped off:
PIR: Insulation Australia (NSW/QLD/VIC). 75mm PIR: $12-$14/sqm installed. They do the whole job.
Wool: Eco Insulation (VIC). 50mm wool: $18/sqm installed. Only if you're in Melbourne and want to feel good about yourself.
Spray Foam: Insulfoam (NSW). Closed cell: $22/sqm. Get a quote. Don't DIY it. You'll regret it.
Bottom line: PIR is the only insulation that makes sense for 95% of Aussie off-grid Sprinter vans. Spray foam is for people with cash to burn. Wool is for people who care more about "eco" than comfort. Get PIR. Install it right. Stop overcomplicating it.
When to Call a Professional
While many off-grid projects are achievable as DIY, certain situations require licensed professionals:
Electrical work beyond basic 12V DC additions — requires a licensed electrician
Structural modifications to buildings or load-bearing elements
Gas line installation or modification
Solar array installations above safe voltage thresholds
Any work that affects the structural integrity of your property
Always check local regulations and obtain necessary permits before commencing work.
It walks you through the real‑world difference between spray foam and batt, and shows the prep steps and temperature‑control tips you need before cutting any panels.— Mick O'Brien
