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H1 Calculation Method Checker

H1 Energy Efficiency

H1 Calculation Method Checker

Since 27 November 2025, the Calculation Method is the Acceptable Solution path for the energy efficiency of houses and small buildings – the Schedule Method has been removed. Enter each element’s area and construction R-value, pick your climate zone, and check whether the design’s heat loss sits under the reference building. Enter your details and we’ll email your result.

What this checks

It runs the H1/AS1 6th edition Calculation Method. Your building’s total heat loss is the sum of each element’s area divided by its construction R-value, and it has to sit at or below a reference building for your climate zone. The tool checks:

  • Whether proposed heat loss is at or below the reference building for your climate zone
  • That wall glazing stays within 40% of the gross wall area – above that, the design moves to the Modelling Method (H1/VM1)
  • The minimum construction R-values that still apply as floors: roof R2.6, walls R1.0, other floors R1.3
  • Your climate zone (1 to 6), set from the territorial authority under H1/AS1 Table C.1.1.2

💡 Designer tip: the R-value that counts is the construction R-value – the whole build-up, framing and linings included – not the figure on the insulation packet. Work them out with NZS 4214 and H1/AS1 Appendices D and E, or the BRANZ House Insulation Guide 6th edition. The 5th-edition guide uses different methods for slabs, windows and doors, so don’t mix editions.

Please note: this tool follows the Calculation Method in H1/AS1 6th edition (effective 27 November 2025). The 5th edition – with the now-removed Schedule Method – can still be cited for consents lodged up to 26 November 2026. Passing the Calculation Method demonstrates clause H1.3.1(a) and satisfies the Building Performance Index (H1.3.2E); it does not cover hot water, HVAC, or heated floors, walls and ceilings, which are assessed separately. This is an indication for design, not a compliance determination – your Licensed Building Practitioner or council makes the call. See MBIE Building Performance and BRANZ.

Common questions

What changed between the Schedule Method and the Calculation Method?

The Schedule Method set fixed minimum R-values element by element, with no trade-offs, and was removed in the 6th edition on 27 November 2025. The Calculation Method compares your design’s total heat loss against a reference building for your climate zone, so extra insulation in one element can offset another – provided the total stays under the reference and the minimum R-values (roof R2.6, wall R1.0, other floors R1.3) are met.

Can I use the Calculation Method with a lot of glazing?

Up to 40% of the gross wall area. Above 40%, the Calculation Method can’t be used and the design moves to the Modelling Method (H1/VM1).

Does this check cover all of H1?

No. It covers the thermal envelope (clause H1.3.1(a)), which also satisfies the Building Performance Index. Hot water, HVAC, and heated floors, walls and ceilings have their own H1 requirements and are assessed separately.

Getting the thermal envelope right early avoids redesign at consent. We build H1 into the design from the first sketch.

Talk to our design team