In my Detailed Blog of March 2025, 'Considering the Review of NZ Building Code Clause H1 Energy Efficiency' I briefly describe and comment on the three current methods (Schedule, Calculation and Modelling) of demonstrating Building Consent compliance with NZBC-H1, and some of the complications involved with any future changes.

In a Press Release dated 3rd July 2025 the Minister, Hon. Chris Penk, advised that MBIE “… will remove the current Schedule Method in favour of more flexible alternatives.”. The press release also updates his other thinking on the need for a review of the NZBC-H1 requirements. Included is advice that officials have been directed “… to explore designating the Far North as a separate climate zone under the Building Code.”, and that MBIE will consult the public “…before final decisions are made...”.

I await with interest the outcome and recommendations to be reached by MBIE, especially as the specific Construction R-values of the Schedule Method for the listed elements of the dwelling will be removed with significant consequences for the other two Methods. There seems to be a widespread assumption that these construction R-values are the precise values to be achieved if compliance is to be gained by the Schedule Method. The actual requirement is that the listed construction R-values are minimums as stated in NZBC-H1/AS1: “Minimum R-values: Each individual building element (walls, roof, floor, etc.) must have an R-value greater than or equal to the minimum required by the relevant schedule.”

When directly asked, I’m sure virtually all building industry personnel involved with H1 will immediately agree that the R-values are minimums, not absolutes. With a bit of manipulation, the Calculation and Modelling Methods can still show H1 compliance when the R-value of a particular element is below the Schedule Method minimum.

At present the Calculation Method uses the construction R-values of the Schedule Method tables as the denominators in the calculation formula. With the removal of the Schedule Method tables, what evidence-based R-values will be used as the denominators?

At present when demonstrating compliance with NZBC-H1 by the Verification Method, H1/VM1, the basic principle is that the annual heating and cooling loads of the Proposed Building shall not exceed that of the Reference Building. The two buildings are to be the same except for the construction R-values of the thermal envelope elements (and window areas and locations). At present the relevant R-values for the Reference Building are the same figures as those given for the Schedule Method. With the removal of the Schedule Method figures, what evidence-based R-values will be used for the thermal envelope of the Reference Building?

If one reason for the removal of the Schedule Method is the inadequacy of the current Construction R-values then the replacement evidence-based figures for the Calculation and Modelling Methods will need to be such that significantly better heating and cooling performance for our future housing stock is achieved.