Regression-based sensitivity analysis of key building parameters influencing indoor overheating in existing residential buildings under future climates

Climate change is intensifying the frequency, duration, and severity of heatwaves, increasing the risk of indoor overheating in residential buildings. Housing stocks in cold climates are particularly exposed, as they were predominantly designed to minimise winter heat losses rather than dissipate excess summer heat, limiting their adaptive capacity under future warming. This study assesses summer indoor overheating in an existing cold-climate residential dwelling in Gdynia, Poland, and quantifies the influence of key building parameters using regression-based sensitivity analysis. Building performance simulations were conducted for six future climate scenarios (2030–2090) under RCP 4.5 and RCP 8.5 and compared with a current baseline climate. Indoor overheating was evaluated using three thermal resilience indicators capturing duration, frequency, and severity: Time of Overheating (To), Percentage of Overheating (Po), and Indoor Overheating Degree (IOD). Results demonstrate systematic increases in overheating across all future scenarios, with a disproportionate escalation in cumulative severity relative to duration and frequency, particularly under late-century RCP 8.5 conditions. Regression-based sensitivity analysis identifies solar heat gains through glazing as the dominant driver of overheating across all scenarios. Ventilation acts as a secondary but climate-dependent lever, while infiltration and envelope conductive properties exhibit limited influence within the tested parameter ranges. Results also indicate declining mitigation leverage of individual passive measures under progressively warmer climates, underscoring the need for prioritised and integrated retrofit strategies. The study provides quantitative evidence to support the assessment of overheating resilience and retrofit decision-making under future climate scenarios.