NatHERS - Nationwide House Energy Rating Scheme

For more details, see: www.nathers.gov.au

Summary of HERS software tools

House energy rating assessors use thermal simulation computer programs to determine if a house is energy efficient. The software packages endorsed by the Building Code of Australia to rate residential dwellings are based on the software engine that was developed by CSIRO. SEDO recommends using the second-generation HERS software to obtain a rating, as the second generation software is more powerful and more accurate.  Three second generation HERS software tools are available:

• FirstRate 5
• AccuRate
• BERS Pro

Each tool offers a larger materials database than has been previously available, improved ventilation modeling, and is able to be used for a large range of house types in all parts of Western Australia.  Western Australian house energy rating assessors are listed on the National Assessor Register.

How Does the HERS Engine Work?

The house is divided into zones for living and sleeping and areas that do not need heating or cooling. Bedrooms do not generally need to be kept as warm as living areas, and garages and laundries rarely need to be heated or cooled in comparison to bedrooms and living areas.

The size of each of these areas, the external and internal walls and the windows is measured. This information is entered into the computer along with details about the building materials used for walls, roof and floor and whether insulation will be used. The direction that the building is facing is needed, as well as the postcode to determine the relevant climate zone.

In just a few minutes the program goes through every hour of every day of a typical year for that climate zone. It looks at how the temperature changes throughout the day and calculates if the house will get too cold or too hot and how much energy will be needed to keep it comfortable. A report is produced which shows the amount of energy needed for summer and for winter, and compares the house with others to give it an energy efficiency rating.

The program does not take into account the efficiency of appliances and equipment. Information about the efficiency and costs of appliances is available at www.energyrating.gov.au.

All of these software tools use the same HERS engine and are subject to detailed validation processes by NatHERS.  All software is constantly under review to incorporate a wider range of data, climates zones and building techniques.

FirstRate 5

FirstRate was developed by the Sustainable Energy Authority Victoria.   More information on the FirstRate software and a demonstration version can be found on the Sustainability Victoria website. 

Note that from 1 May 2009, assessors will no longer be able to use first generation (FirstRate version 4) software to provide house energy ratings.

AccuRate

The AccuRate software was produced by CSIRO, Division of Building, Construction and Engineering . AccuRate is the upgraded second generation version of what was previously known as 'NatHERS'.   AccuRate software is available from Hearne Scientific at: www.hearne.com.au.

Building Energy Rating Software (BERS)

BERS was developed in Queensland by Dr Holger Wilraith. Second generation BERS is based on AccuRate and has a simplified graphical user interface, along with some additional features. More information about BERS can be found on the Solarlogic site.

Association of Building Sustainability Asssessors (ABSA)

The Association of Building Sustainability Assessors (ABSA) administers the National Assessor Register and maintains the website that assessors use to submit House Energy Efficiency Assessments on-line. ABSA is a 'not-for-profit industry-owned and directed' association that aims to deliver the highest standard of excellence to the practice of sustainability in Australian buildings.

SEDO works with ABSA to ensure a high quality of NatHERS assessments within Western Australia.   ABSA covers the administration, training and technical support for building assessors that use any of the Australian building sustainability software tools (including NatHERS, FirstRate, AccuRate, BERS, and BASIX).

Assessors must complete rigorous training and examination, and are subject to auditing. To be a member of ABSA, assessors must also be backed by Professional Indemnity Insurance and meet ABSA requirements for quality assurance and continuing professional development. ABSA's services also include: advice and information for Councils, building professionals and consumers and seminars on sustainable development.

More information can be found at www.absa.net.au.

ABSA National Assessor Register

Assessors are 'appropriately qualified persons' for the purposes of providing evidence, in the form of an 'Assessor's Certificate', of compliance with Building Code of Australia Energy Efficiency for Class 1, Class 2 and Class 4 buildings.

These assessors have received appropriate training in the use of the software, as well as in building thermal performance theory. Assessors operate under an industry Code of Practice and at least one of each assessor's ratings is audited annually.

National registration is delivered 'on-line', which means that 'Notices of Ratings'; advice on fee renewal and collection; auditing; certificate management; and statistical performance monitoring are largely automated.  If you would like to become an assessor, visit the Becoming An Assessor page.