Overheating causes in cold regions’ residences under evoling building regulations: Focusing on field investigation and simulation of envelope performance

Due to global climate change, summer overheating poses an increasing risk to residential buildings in severe cold and cold regions of China. However, building envelope design and regulations in these regions have not yet adequately responded to this risk. Focusing on samples from different periods subject to different building regulations, this study conducted a three-year field survey to assess the degree of summer overheating in 24 north-facing bedrooms with 11 envelope types in 13 representative Chinese cities. Additionally, small-scale models were used to analyse indoor temperature variations for heavy, medium, and light thermal mass envelopes. Further simulations examined the relationship between thermal performance and overheating, while also exploring the potential impact of effected by evoling building regulations on overheating. During summer heat in severe cold regions, buildings with low U-value envelopes (built after 2010) experienced an average of 110 more hours of overheating than those with high U-value envelopes. Monitoring of small-scale models indicated that heavy thermal mass envelopes maintained the most stable indoor thermal environment, with daily average temperature fluctuations of 1.96 °C, 4.07 °C, and 12.15 °C for envelopes with heavy, medium, and light thermal mass, respectively. The simulation results indicated that with evolving building regulations, reducing the U-value led to an increase in overheating duration of 6.03 %–22.42 %. The assessment revealed that envelopes with low U-values and light thermal mass may be responsible for the risk of overheating in cold regions. The stringent requirements imposed by China's current building regulations may exacerbate this risk.