What Is R-Value in Insulation? Australian Targets, Costs & NCC Minimums
R-value measures how well insulation resists heat flow — the higher the R-value, the better the insulation. R6.0 ceiling batts resist heat transfer twice as well as R3.0. Australia uses metric R (m²·K/W), so US "R-30" ≈ metric R5.3. Below: exactly what R-value you need for NCC 2022 and 7-star NatHERS by climate zone, plus 2026 install costs from $5–$12/m² for ceilings.
NCC 2022 R-value minimums (residential)
| Element | Cool (Melb/Hob) | Mixed (Syd/Adel) | Warm (Bris/Perth) | Hot (Darwin) |
|---|---|---|---|---|
| Ceiling | R7.0 | R6.0 | R5.0 | R4.1 |
| External wall | R4.0 | R2.8 | R2.8 | R3.8 |
| Suspended floor | R3.5 | R2.5 | R2.5 | R2.5 |
| Slab edge | R2.0 | R1.0 | R1.0 | R1.0 |
Indicative DTS values — your NatHERS modelling may justify lower or require higher R-values depending on glazing and orientation.
Install costs (2026)
- • R6.0 ceiling batts: $5 – $12/m²
- • R2.5 wall batts (new build): $8 – $15/m²
- • Blown-in wall retrofit: $25 – $60/m²
- • Underfloor batts: $20 – $45/m²
- • Whole-home retrofit: $4,000 – $12,000
Priorities
- 1. Ceiling first — 25–35% of heat loss
- 2. Draught seal — see guide
- 3. Walls — 15–25% of heat loss
- 4. Floors — 10–20% of heat loss
- 5. Windows — Low-E glazing
Model your insulation upgrade first
A NatHERS existing-home assessment shows the exact R-value uplift you need for the biggest bill and comfort gains — so you don't over-spec.
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