Getting to grips with ALF 3.2

By - , Build 114

ALF has been the topic of many calls to the BRANZ helpline recently. This overview should get you started with ALF 3.2, and future issues of Build will answer some of the more detailed questions asked.

The BRANZ Annual Loss Factor tool (ALF 3.2) is a free online aid to the thermal design of houses. It is presented in a step-by-step format and provides a method of calculating the energy performance of conventional New Zealand houses.

It is also a Verification Method for determining the Building Performance Index (BPI), which can be used to show compliance with New Zealand Building Code Clause H1 Energy efficiency. ALF 3.2 can be found in the BRANZ Toolbox on the website www.branz.co.nz.

ALF allows comparison of up to 30 building designs

A range of building designs can be loaded into the computer, and ALF evaluates them for heating energy efficiency. Each project in ALF can contain up to 30 different designs. These can be compared against each other. You can store and evaluate different thermal design features of any building, such as:

  • insulation levels
  • different window types
  • various building orientations
  • different levels of thermal mass
  • other design options.

The ALF program has two sections – design and results.

First, the design section

The design section is where you enter data on the building design, climate and heating behaviour of the occupants. This includes the construction details and insulation levels of the walls, floors, roofs (including skylights) and windows that make up the thermal envelope of the house.

The thermal envelope is made up of the components of the house that keep the heat in, assuming the whole house is heated. For a house with no garage attached, all the rooms are within the thermal envelope. Where an unheated space is attached to the house, such as a garage or utility shed, the walls between the garage or shed and the living space become the line of the thermal envelope, that is, the external wall for insulation purposes.

Input on the building’s orientation, thermal mass properties and ventilation/air infiltration are also required for the ALF calculation.

Results section shows performance

The results section shows how the building described in the design section performs in terms of heating energy consumption. Each page in the results section contains different aspects and details of the thermal performance, such as tabulated heat losses through different components.

It also provides the Building Performance Index for the design and checks whether it is compliant with the New Zealand Building Code. To use the Building Performance Index for Code compliance, you will need to provide the Building Consent Authority with a copy of the ALF report when submitting the plans.

For more

There are online help files (accessed via the top menu bar). If you need further assistance, the building industry can call the BRANZ helpline on 0800 80 80 85 and the public can call 0900 5 90 90 (these calls cost $1.99/min + GST).

Download the PDF

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Articles are correct at the time of publication but may have since become outdated.

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