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The cost question everyone asks — but not everyone answers honestly
When builders compare cavity wall insulation costs, they usually compare batt prices. R2.7 batts cost this much per square metre. R2.0 batts cost that much. Decision made.
But the batt is only part of the wall assembly cost. The thermal break, the installation labour, and the long-term liability risk all factor into the real number. And the relationship between the thermal break and the batts is where most builders leave money on the table.
Wall insulation batt costs (est. RRP, 2026)
That $13.23 per square metre difference is real money. On a standard home with approximately 150–200sqm of external wall area, that’s $1,985–$2,646 saved on batts alone. Multiply that across 30 homes a year and you’re looking at $59,000–$79,000 in annual insulation savings.
How is this possible?
Total Wall R Value is a calculation that accounts for the thermal performance of the entire wall assembly, including the thermal bridging across the frame — not just the batts. The thermal break R-value is a direct input to this calculation.
When the thermal break has a higher R-value, the batts don’t need to work as hard to achieve the same Total Wall R Value. An R0.58 thermal break with R2.0 batts can achieve the same or better Total Wall R Value as an R0.2 thermal break with R2.7 batts.
Most designers or builders don’t have this modelled because nobody tells them to. They spec the batt based on habit, use whatever thermal break their supplier stocks, and never run the numbers on the full assembly. It’s not a knowledge gap — it’s an information gap.
What many designers and builders don’t realise is that you can increase the R-value of the thermal break in NatHERS modelling tools like Hero, FirstRate5, and BERS Pro. This directly affects the star rating calculation.
The cost of NOT changing your approach
The immediate cost is overspending on batts. But the indirect costs can be larger:
Condensation liability. An R0.2 thermal break at 12mm depth doesn’t create an effective drained and ventilated cavity. Moisture accumulates in the wall. By the time you see the damage — structural rot, mould, ghosting on cladding — the repair cost dwarfs any batt savings.
Missed opportunity on star ratings. OR, you could leave the R2.7 batts in the wall and use the higher thermal break R-value to reduce ceiling insulation, achieve savings on glazing options, or deliver your client a higher rating home. A higher-performing thermal break gives you choices beyond minimum compliance.
Overseas precedent. The UK and New Zealand experience has shown that when wall failures occur at scale, the financial consequences for builders are substantial. Australia’s regulatory trajectory is following the same path.
What about the thermal break cost?
Builders sometimes ask whether a higher-R thermal break costs more than a basic one. It does — but the insulation savings more than offset the difference. The net result is a lower total wall material cost AND better thermal performance AND condensation management.
And because self-adhesive XPS strips require no tools, no fixings, and no power cutting on site, the installation labour cost is lower than screw-fixing timber battens or cutting plywood to width.
Running the numbers for your builds
Every builder’s cost structure is different. Wall areas vary. Climate zones affect batt requirements. Material pricing shifts by region and supplier.
ATI’s free Total Wall R-Value Comparison tool lets you model your actual wall assembly. Input your current thermal break and batt specification, compare it against an optimised combination, and see the per-sqm and per-home savings for your builds.
Cavi-Break®: R-value 0.58. 3x the NCC minimum. Self-adhesive 20mm XPS.
Builders like Philip Usher Constructions and OJ Pippin Homes have adopted the system and reported lower project costs and faster installation. Request a sample and run the numbers for your next project.
Your next step
Use the Total Wall R-Value Comparison tool. See what your current wall assembly actually costs you — and what it could cost with an optimised thermal break specification.
Then request a sample from ATI. Try it on one project and decide for yourself.
Australian Thermal Industries manufactures Cavi-Break® and Cavi-Vent® — high-performance thermal break and cavity ventilation systems for Australian residential and light commercial construction. 10-year warranty. 100% recyclable. Independently tested.
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