Climate-resilient retrofitting for Australian homes: A parametric analysis of future performance and overheating risk

• Assesses climate-resilient retrofit strategies for Australian homes under future warming. • A brute-force analysis parametrically evaluates 120,960 designs and climate scenarios. • Performance is evaluated for both annual energy use and thermal resilience during heatwaves. • Identifies a critical risk of maladaptation where present-optimised retrofits fail in the future. • Advocates for integrated, climate-specific strategies that combine passive and adaptive measures. This study evaluates climate-resilient retrofit strategies for existing Australian homes, using projected 2050s weather data under future moderate (RCP4.5) and high-emission (RCP8.5) scenarios. To this end, a brute-force parametric analysis was employed, simulating 120,960 unique retrofit combinations (envelope insulation, exterior colour, fenestration upgrade, and the application of ceiling fans) for a representative building archetype. The assessment covered annual heating/cooling energy consumption and thermal resilience, a home’s ability to maintain safe conditions during extreme events, across four distinct climate zones (Brisbane, Canberra, Melbourne, and Sydney). Results show a climate-driven shift in retrofit priorities and achievable benchmarks. In warmer climates, rising cooling loads dominate: Brisbane’s median star rating for the entire design population falls from 5.6 (present) to 2.9 (2050s-RCP8.5), and even the most optimised design fails to meet Australia’s national 7-star energy performance benchmark by mid-century. Conversely, in cooler climates (Canberra, Melbourne), reduced winter demand initially improves annual performance (>30 % heating reduction), before it reaches a turning point where future cooling loads rise and negate these benefits. Thus, the configuration of an optimised retrofit design is not static but must evolve in response to climate change. While a highly insulated and airtight building envelope improves annual energy performance, it can pose severe overheating risks during power outages. However, pairing this high-performance envelope with adaptive strategies (natural ventilation) proves transformative, significantly enhancing passive survivability during future heatwaves. Ultimately, a holistic, systems-based approach that integrates passive measures and adaptive strategies is essential to ensure that retrofitted homes are not only energy-efficient year-round but also safe and climate-resilient in the face of extreme future conditions.