A comparison of accredited second generation NatHERS software tools
Authors: Williamson, Terry; Orkina, Nina; Bennetts, Helen
The Building Code of Australia (BCA) energy-efficiency regulations for houses provide deemed-to-satisfy acceptable construction solutions, and verification using computer simulation software approved by the Nationwide House Energy Rating Scheme (NatHERS). From 1st May 2009 only second generation software is referenced in the BCA. In 2006 NatHERS introduced a substantially upgraded “second generation software” package AccuRate (Version 1.0) developed by CSIRO. A software Accreditation Protocol allows other software to be used in NatHERS. FirstRate5, developed and marketed by the Victorian Government’s Sustainable Energy Authority and BERS Pro, developed by SolarLogic in Queensland have been granted provisional accreditation.
In several jurisdictions any of these programs may be used to demonstrate building code compliance therefore the consistency of results is of utmost importance.
The first part of this paper introduces some background to the NatHERS scheme and the accredited software.
Then, to gauge the consistency of results a number of standard project dwellings are assessed using the three programs and the results compared. Secondly, using a benchmark BESTEST type building model, results for the three accredited programs are compared for a number of variations in configuration and construction. These include the effects of zoning (including attics and sub-floor zones), as well as, the effects of thermal mass and insulation, solar gain via windows, window-shading, infiltration, etc.
The paper concludes with a discussion of the results and the implications for using the software to demonstrate regulatory compliance.