Enhancing building energy performance and climate resilience with phase change materials and reflective coatings

Enhancing energy efficiency in residential buildings is essential for reducing CO₂ emissions and meeting the growing demands of global energy standards. This study investigates the impacts of retrofitting existing Australian houses with phase change materials (PCMs) and reflective coatings on annual energy savings, star ratings and performance during heatwaves. Experimental results demonstrate that applying PCM boards to walls, ceilings or both resulted in a maximum reduction of peak indoor air temperature by 5.8 °C when both surfaces were treated, allowing a peak load shift of up to 71 min into the off-peak period. The study evaluates the energy performance of retrofitted houses in Sydney, Alice Springs, and Darwin. Using experimental data and validated EnergyPlus simulations, optimal retrofit configurations achieved annual energy savings of 31.9 kWh/m²·y in Sydney, 60.6 kWh/m²·y in Alice Springs, and 85.6 kWh/m²·y in Darwin, corresponding to improved star ratings of 7.0, 7.1, and 7.6, respectively. During heatwaves, retrofitted houses experienced significant reductions in thermal discomfort, achieving 100 % in Sydney, 86.7 % in Alice Springs and 92.6 % in Darwin. Economic analysis revealed payback periods ranging from 5.3 to 24 years, depending on local climate conditions. These findings underscore the feasibility and effectiveness of retrofitting strategies to enhance energy efficiency, improve thermal comfort and achieve Australia's 7-star energy standard.