Summer thermal comfort in naturally ventilated residences during overheating: A multi-city field investigation in China’s cold and severe cold regions

Despite growing concerns over summer overheating in China’s cold climate regions, research has predominantly prioritized winter comfort and heating energy demand. Empirical evidence on how residents perceive and adapt to summer heat remains critically limited. This study investigated summer thermal comfort and adaptive behaviors in overheating-prone residential buildings across multiple Chinese cities through a large-scale field survey involving 11,884 valid questionnaires and environmental monitoring. The study analyzed interactions between thermal environments and occupant responses, focusing on short-term thermal history, clothing adjustments, and diurnal variations in thermal sensation. The results indicated widespread overheating, with 37 of the 44 monitored rooms (84.1%) exceeding the CIBSE TM59 threshold based on operative temperature data collected from May to September 2024. Regression analysis revealed a neutral temperature of 23.5 °C, with comfort at 24.4 °C and an 80% acceptability limit of 28.7 °C, defining a practical overheating benchmark for cold-region residences. Clothing adjustment proved effective in maintaining comfort within ±3∼4 °C of the neutral temperature. Individuals exhibited a preference for neutral to marginally warm environments and displayed greater adaptability in warmer conditions. Short-term thermal history—especially recent cooling—strongly affected thermal sensation, although behavioral responses were limited. Neutral temperatures were ∼2 °C higher at night than during the day, underscoring the need to account for behavioral adaptation and temporal variation in comfort assessments. This study offers empirical data and insights to inform overheating risk evaluation and thermal environment design in China’s cold and severe cold regions, where summer indoor comfort has long been overlooked.