Retrofitting for the future: Analysing the sensitivity of various retrofits to future climate scenarios while maintaining thermal comfort

Significant research has explored the impact of future climate scenarios on building energy loads; however, few studies have considered the efficiency of envelop retrofits under a changing climate and most have a very limited geographic scope. Using a range of future climate scenarios based on global average temperature rise, rather than specific models, this paper presents a multi-region, multi-scenario analysis of retrofits for large office buildings for two ASHRAE climate zones. Three levels of envelope intervention were developed based on currently available materials and current practices to explore the individual and combined impacts of increased roof and wall insulation, and glazing replacement. The simulations used the ASHRAE 90.1–2019 prototypical building model equipped with a variable air volume (VAV) HVAC system served by electric chillers with a reference COP of 6.28 and natural gas boilers with a nominal thermal efficiency of 81.25%. These were simulated in each climate scenario and total heating and cooling energy were compared with the unmodified ASHRAE 90.1–2019 prototypical building model. Thermal comfort was also considered through unmet hours to ensure like-for-like comparison. All retrofits tested demonstrated high sensitivity to climate change, with energy use increasing by up to 18% for cooling and decreasing by up to 41% for heating. By analysing the outputs using regression models, a series of equations were developed to predict retrofit impacts as a function of future climate change. Increased insulation—in roof and wall—beyond the baseline was found to have limited benefit while glazing replacement offered significant value.