Other Resources

Providing independent information and links to guidelines and tools to help design and construct sustainable buildings.

Energy Performance Tools

A number of New Zealand-focused energy performance and design tools are available to help you design energy efficient buildings and assess their performance.

Annual Loss Factor (ALF)

Annual Loss Factor (ALF) is a BRANZ tool for determining the Building Performance Index (BPI) of a house design. It can demonstrate compliance with Building Code clause H1.3.2E (“Buildings must be constructed to ensure that their building performance index does not exceed 1.55.”)
However, under Building Code verification method H1/VM1 (5th edition, effective 29 November 2021 with a 1-year transition period), compliance with clause H1.3.2E is no longer sufficient for demonstrating compliance with clause H1.3.1(a) (“The building envelope enclosing spaces where the temperature or humidity (or both) are modified must be constructed to ­– (a) provide adequate thermal resistance…”). In effect this means that from 3 November 2022, an ALF calculation alone will not be enough to show that a house complies with all the requirements of Building Code clause H1.

NZS 4218:2009 Calculation Method Tool

This tool on the BRANZ website calculates heat loss for the Calculation Method of NZS 4218:2009 Thermal insulation – Housing and small buildings. Designers select the climate zone, wall construction type(s) and so on, and the tool applies the Calculation Method automatically, showing whether the details pass or fail compliance requirements. The tool may be used as an Alternative Method for demonstrating compliance.


This BRANZ resource provides actual cost and return data for performance improvements for new homes in the areas of comfortable temperatures, energy efficiency and water management. Figures are available for nine climate zones, from Auckland to Invercargill.

The performance upgrades are based on independent research and are region-specific where possible. Only the most cost-effective improvements have been selected. All figures are estimates and should be seen as starting points for discussions.

The resource can be used in conjunction with ALF and the Photovoltaic Generation Calculator. You can find more information here.

Carbon calculators/tools

Toitū Envirocare (a subsidiary of Manaaki Whenua – Landcare Research, a Government-owned Crown Research Institute) provides information on independent carbon audits and third-party certification. Its carbonzero and carbonreduce certification programmes are accredited by the Joint Accreditation System of Australia and New Zealand (JAS-ANZ) and were the world’s first carbon certification programme to be accredited under ISO 14065.

Performance monitoring

Monitoring the performance of a house is critical to ensure that all systems are running as they should be. BRANZ Senior Sustainable Building Scientist Roman Jaques suggests some ideas for getting started.

Photovoltaic generation calculator

A household can generate its own electricity from sunlight with a photovoltaic system on the roof. The Toolbox on the BRANZ website has a photovoltaic generation calculator that can tell you how much electricity a PV system can produce. Just enter a few facts about the size of system, whether it is flat or inclined, how far away from facing north it is and so on, and at the click of a button, you can find out how much power you can expect it to generate.

Window Energy Efficiency Rating System (WEERS)

The design and installation of windows has a major impact on a building's energy efficiency with up to 40% of heat loss being through glass. Windows affect how much energy buildings use, how warm or cold they are and how comfortable they are for the occupants.
When replacing glazing, one tool that can help is the Window Energy Efficiency Rating System (WEERS), a 6-star rating system. WEERS combines the thermal performance of the frame and glazing, together with the size
 of the window, to calculate an individual thermal performance rating RW for each window.

You can find more information in BRANZ Bulletin 579 WEERS – Window Energy Efficiency Rating System.



Thermal simulation tools

Simulation software can measure the impact that design decisions are likely to have on the thermal performance of a building. They can guide a designer to the optimal passive design for a project. Some of the main international software tools available are discussed on the thermal simulation page.

2021/2022 Upgrade to H1

Note that significant changes to the Building Code clause H1 Energy efficiency were introduced on 29 November 2021. They will require higher levels of thermal performance in new buildings. The three existing climate zones will be replaced by six zones. The changes will become mandatory in November 2022, with a further upgrade for window performance in the warmest climate zones in 2023.



Updated: 13 December 2021