What is H1 of the Building Code and why does it matter?
Short answer
H1 is the Building Code clause that sets minimum thermal performance for new residential buildings — insulation R-values for roof, walls, floors, and windows. Since the 2022/2023 H1 update (rolled out in stages through 2024), the standards are significantly stricter and split NZ into six climate zones with different minimums per zone. It directly affects build cost and is a common consent RFI trigger.
Key facts
- Six climate zones replace the older three-zone system
- Roof R-values range from R6.6 (zone 1) to R6.6 (zone 6) — actually now mostly R6.6 nationwide
- Wall R-value: typically R2.0
- Window thermal performance: ranges from R0.37 to R0.50
- Affects glazing choice (double vs thermally-broken double or triple)
Why H1 made builds more expensive
Thicker insulation, often thicker wall framing to fit it (e.g., 140mm framing in zones requiring R2.6+). Double-glazing is now the floor; thermally-broken aluminium or PVC frames are common; some builds use triple-glazing.
Builders typically add $15-30k to the per-house cost compared to pre-H1 builds, depending on zone and design.
Compliance routes
Schedule method: meet the R-value table directly. Simpler, common.
Calculation method: model the whole building using an approved tool — gives flexibility (e.g., trade a high-spec window against a lower-spec wall). Used by designers for complex layouts.
Modelling method: full energy modelling (BRANZ ALF or equivalent). Mostly for innovative designs.
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Related questions
Sources: Building Code clause H1 (Acceptable Solution H1/AS1); MBIE — building.govt.nz/h1. General information for NZ homeowners, not legal advice — building rules change and vary by council, so confirm critical details on the official source before acting. Last updated 2026-05.