Investigating envelope retrofitting potential and resilience of Australian residential buildings − A stock modelling approach

Residential buildings consume around 24 percent of overall electricity use in Australia. Though the energy efficiency of new buildings is progressively increasing, there are around 10 million existing homes most with poor thermal and energy performance. Improving these existing homes are imperative for Australia to reach its target of net zero by 2050. This paper adopts a stock modelling approach using real designs of more than two hundred thousand detached dwellings and apartments submitted for certification in eight states and territories across Australia to investigate envelope retrofitting potential of the housing stock. The performance of the existing housing stock was assessed and the effect of various levels of envelope improvements on energy efficiency and overheating were analysed for current and future climatic conditions. With improvements in 10% of the entire building stock, 3.14 Mt, 3.52 Mt and 7.2 Mt CO₂ emission reductions per year respectively were estimated with Rehab, Refurb and Renov improvements. Both detached dwellings and apartments experienced overheating across all the states and territories for the current and future climatic conditions. Though envelope improvement caused some reduction in the overheating, it was not significant. The high average overheating hours in Queensland come from nighttime overheating in the bedrooms, whereas in most other states daytime overheating constitute the majority. Various improvements in the building envelope were effective in reducing daytime overheating reductions rather than nighttime overheating, though the impact was marginal. The results from this study provided guidance on policy and regulatory mechanisms that can be introduced for developing decarbonization pathways for buildings at a national level.