Net-Zero Energy Retrofitting in Perth’s Residential Sector: Key Features and Strategies for Sustainable Building Transformation

The study aims to identify optimum retrofitting strategies that mitigate climate change and support Australia’s net-zero emissions target by 2050. Current heating and cooling demands, as well as the energy performance of three stand-alone houses built before 2003, were evaluated to determine optimal retrofitting measures. Based on a comprehensive literature review and physical building surveys and energy simulations using FirstRate5 of three selected case studies of stand-alone houses in Australia’s climate zone 5, the study identifies and proposes effective retrofitting opportunities in Western Australia. Additionally, the outcomes from FirstRate5 illustrate that improving ceiling and exterior wall insulation in living and dining areas, sealing air leaks, reducing overshading, and replacing single-glazed windows with double-glazed units while enlarging north-facing windows, following the recommended wall–window ratio significantly improve the energy rating of the selected houses. The average energy rating performance of the three selected stand-alone houses increases from an average below 3.5 stars (211.5 MJ/m2) to above 7.5 stars (46.7 MJ/m2), representing around 76.6% improvement in energy efficiency. Just to contextualise the scale up, such retrofitting of all old stand-alone houses built before 2003 would potentially reduce emissions by 12.73 Mt CO2-e/year, representing a 3.16% contribution toward Australia’s national emission reduction target by 2035. Additionally, installing solar energy systems could reduce an extra 4.5 Mt CO2-e/year. The study’s findings demand robust retrofitting strategies for Australia to achieve its 2050 net-zero emissions targets.