H1/AS2 2nd edition calculation method tool
About this tool
The H1/AS2 2nd edition calculation method tool helps designers and building professionals automatically check whether buildings other than housing over 300 m2 meet the energy-efficiency requirements of Building Code clause H1.
It applies the calculation method in H1/AS2 2nd edition and automatically determines whether a building passes or fails based on the information entered. Input data of areas, R-values and SHGC values are entered on relevant sheets for each particular building element type (roof, wall, floor, window, door and skylight) with detailed results provided on a summary page than can be included in building consent documentation.
Download this tool
How to use this tool
To use the H1/AS2 2nd edition calculation method tool:
- Download and open the H1/AS2 Excel tool.
- Read the instructions before entering any data.
- Select the correct climate zone.
- Enter areas and construction R‑values for each building element. For windows and doors the Solar Heat Gain Coefficients (SHGC) need to be entered for each item.
- Enter values only into blue‑shaded cells and use drop‑down options where provided. Review the automatically generated results page to confirm compliance.
The tool performs built‑in checks to:
- prevent R‑values lower than the minimum allowed
- prevent unrealistically high values caused by data entry errors
- automatically calculate pass/fail outcomes.
The results sheet includes all entered data and calculations and is formatted for printing and submission as part of consent documentation.
Background
The calculation method is now the primary compliance pathway for H1/AS2 2nd edition. The schedule method is being phased out and can only be used until 26 November 2026 under the H1/AS2 1st edition.
The calculation method allows more design flexibility than the schedule method, including trade‑offs between different building elements, provided overall performance is met.
The solar aperture is calculated from the SHGC’s of each of the windows and the gross wall area of the building. This solar aperture calculation needs to be less than 0.4.
Designers must enter construction R‑values, not insulation product R‑values. These must be verified separately using approved methods such as:
- BRANZ House insulation guide (6th edition)
- NZS 4214 (as modified by H1/AS2 2nd edition)
- relevant appendices within H1/AS2 2nd edition.
The tool reflects BRANZ’s interpretation of H1/AS2 2nd edition. and must be used in its complete, unmodified form. Accuracy depends on correct user input, and BRANZ does not accept liability for errors arising from incorrect data entry.