The influence of residential framing practices on thermal performance
Authors: Dewsbury, Mark; Wallis, Louise; Fay, Roger; Nolan, Gregory
The adoption of energy efficiency measures in the Building Code of Australia has raised concerns from industry and manufacturing groups, as to the accuracy of the simulation method and the actual thermal performance of residential and commercial buildings. Both industry and government have recognised the need to validate the House Energy Rating (HER) software AccuRate and the NatHERS Gen 2 thermal simulation engine, which has been accepted as Australia’s benchmark software. The University of Tasmania, in collaboration with Forest and Wood Products Australia, the Australian Government, the CSIRO and industry, is undertaking research to validate empirically AccuRate in cool temperate climates.
When simulating a residential building the “Assessor” inputs data for various elements of the buildings fabric. This includes walls, floors, roofs, doors and windows. Each of these elements is given a value for insulation and thermal capacitance based on accepted international values and perceived building practice. This method can cause errors in the analysis and resultant Star Rating of the residence in question if underlying assumptions within the software are not valid. Timber framing factors of residential subfloors, walls and roofs have an impact on the overall resistance value and thermal capacitance of the built fabric. This will be discussed the context of recent experiences with test buildings and current residential construction practices, that directly affect the perceived thermal performance of the built fabric. The findings may provide a stepping stone to the next generation of house energy rating software and building design and construction practice in Australia.