H1 Calculators
We're committed to supporting the industry on its path to better buildings.
NZGBC provides useful calculators to help the sector with demonstrating compliance with Building Code clause H1 Energy Efficiency. We have two H1 calculators:
- For housing of any size, and other buildings up to 300m2, use our H1/AS1 calculation method calculator
- For buildings other than housing that are greater than 300m2, use our H1/AS2 calculation method calculator
These calculators should be used in conjunction with the relevant H1 acceptable solution available from MBIE’s Building Performance website:
H1 Energy efficiency | Building Performance
About the H1 Energy Efficiency compliance methods
There are three compliance methods in the H1 acceptable solutions and verification methods that MBIE has published:
- The ‘schedule method’ is the most basic method which requires for every wall, roof, floor, window and door to have an R-value greater than, or equal to, those specified in a table. These minimum R-values vary by climate zone. The schedule method is often not the most cost-effective way of complying with H1 and is set to be removed on 26 November 2026 when the 5th edition of H1/AS1 and the 1st edition of H1/AS2 can no longer be used for building consent applications.
- The ‘calculation method’ allows projects to trade-off lower R-values in parts of the envelope in return for higher R-values elsewhere.
- The ‘modelling method’ uses computer simulations to compare the annual heat and cooling demand of the building with a reference building having reference R-values. The method has the advantage of allowing users to examine annual running costs and risk of overheating together with H1 compliance. NZGBC has an online energy modelling tool called ECCHO that can be used for this modelling compliance method. See ECCHO.
An NZGBC webinar (together with MBIE and BRANZ) on the 2021 H1 changes can be found here. It gives a short tutorial on the calculation method.
In November 2025, MBIE announced further changes to H1. The most important change was to remove the schedule method. Minor changes were also made to the H1 calculation and modelling methods.
During the transition period through to 26 November 2026, both the previous and new editions of the H1 acceptable solutions and verification methods can be used for building consent applications.
After 26 November, only the new 6th editions of H1/AS1 and H1/VM1 for housing and small buildings, and the new 2nd editions of H1/AS2 and H1/VM2 for large buildings can be used.
Building Code H1/AS1 Calculation Method
The most basic method of complying with the new H1 acceptable solution (AS1) for buildings under 300m2 (i.e. homes) is for every wall, roof, floor, window and door to have an R-value greater than those found in a schedule of R-values - this is known as the 'schedule method'.
The schedule method is often not the most cost-effective way of complying with H1. This is especially true with the tougher roof, floor and window R-values coming into force in November.
The acceptable solution allows projects to trade-off lower R-values in parts of the envelope in return for higher R-values elsewhere. This is known as the calculation method.