ALF 4.0

About ALF and contact us

ALF is a simple way to calculate the energy performance of detached New Zealand houses.

ALF (Annual Loss Factor) is a tool for determining the Building Performance Index (BPI) of a house design. It can be used to show compliance with New Zealand Building Code clause H1 - Energy efficiency.

ALF allows you to compare up to 30 different house designs for heating energy efficiency. Different features such as insulation levels, window types and building orientation can be evaluated.

ALF is a single zone model. Internal floors/ceilings in multi-storey houses are not considered for heat losses, for example, but they are considered for the calculation of thermal mass.

ALF has 2 main tabs – Enter data and Results & reports.

In the Enter data tab, you enter data on the house design, climate and the heating behaviour of the occupants. You also enter data about building components such as floors, walls and windows, roofs and other features.

The Results & reports tab shows the heating energy consumption of the building design. Graph shows the gains and losses for each different building element, guiding where changes can be made to improve the thermal performance of a design. 

A full report, including confirmation of H1 compliance, can be saved as a PDF or printed.

A moisture tab gives an assessment of the likelihood of mould.

ALF can also be used to assess and improve the thermal performance of existing buildings.

A new bulletin has been published about ALF4.0 - ALF4 building performance index calculator, BU629. The bulletin covers the following areas of ALF4.0:

  • Getting started;
  • Entering data to find the BPI;
  • Results and reports; 
  • Improving/optimising energy efficiency in design;
  • Energy cost and moisture;
  • Using ALF4 for existing houses;
  • ALF4 web browser requirements.

Contact us

You can contact BRANZ with any questions or feedback you have about ALF4.0 by using

Front page image reproduced with permission from Alpine Image Company Ltd.