University of Tasmania

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An empirical validation of the house energy rating software AccuRate for residential buildings in cool temperate climates of Australia

posted on 2023-05-26, 01:52 authored by Geard, D
In 2003, the Building Code of Australia (BCA) introduced its first thermal performance requirements for residential buildings as a means to reduce Australia's energy consumption and greenhouse gas emissions in the construction sector. This mandated a minimum energy performance rating of 4 stars for all new residential buildings. This requirement was increased to 5 stars in 2006 and to 6 stars in 2010. The introduction of the 4-star requirement had only a minor impact on construction practices and construction costs. However, the adjustment to 5 and 6-star ratings resulted in changes within the building industry, particularly on timber floor construction. The BCA's requirements for increased star ratings and energy efficiency resulted in concerns within the building industry, one of which was in relation to the accuracy of the House Energy Rating scheme's (HER) software \AccuRate\" and its capability to model the building envelope and provide the star rating. AccuRate was developed gradually over a number of years by the CSIRO and was primarily used by building designers as a design tool. When the energy efficiency section was incorporated into the BCA as part of the building approval requirements AccuRate was developed into a regulatory tool. Consequently industry and government have recognized the need to validate this software empirically. The University of Tasmania in collaboration with Forest and Wood Products Australia the Australian Government and housing developer Wilson Homes constructed three test houses in Kingston Hobart for the purpose of validating AccuRate empirically for the cool temperate climate zones of Australia. The test houses were built to standard building practices comprising: brick veneer walls aluminum-framed windows and Colorbond steel roofing. Two houses have suspended timber floors and the third house has a concrete slab floor. An extensive array of instruments and data loggers was installed to measure and document the thermal performance of the three houses. Comprehensive AccuRate simulations of the test houses were carried out and hourly measured and simulated data were compared. The research presents the findings of the graphical and statistical analysis of the variation between the simulated and measured data from the three test houses. The findings demonstrate that while simulated and measured temperatures had comparable profiles for most zones of the three houses individual hourly simulated temperatures did not in most cases match the measured temperatures and were at times quite dissimilar.Simulated temperature ranges were larger in all zones of the houses than measured values. Simulated temperatures were closer to measured values in the slab floor house than in the two timber floor houses. In addition simulated temperatures were closest to measured values in the living room and bedrooms of the concrete slab floor house and were furthest away from measured values in the hall way and roof space of all three houses and in the subfloor space of the timber floor houses. The large discrepancies between simulated and measured temperatures in these spaces of the houses require further investigation and resolution for the continuing improvement and calibration of the AccuRate software. The considerable disagreement of temperatures between simulated and measured values will significantly compromise the accuracy of the heating and cooling loads and consequently the star rating of the software."


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