As the impact of climate change intensifies, meeting the energy demand of buildings in China’s cold regions is becoming increasingly challenging, particularly in terms of cooling energy consumption. The effectiveness of integrating phase change material (PCM) into building envelopes for energy saving in China’s cold regions is unclear. The aim of this study is to assess the effectiveness of PCM integration in building enclosures for energy efficiency in these regions. The research monitored and recorded indoor temperature data from typical residential cases from May to September. This measured data was then used to validate the accuracy of EnergyPlus22-1 software simulation models. Subsequently, the calibrated model was utilized to conduct a comparative analysis on the effects of PCM on indoor temperatures and cooling energy consumption across these regions. The results of these comparative analyses indicated that PCM can alleviate indoor overheating to varying degrees in severe cold regions of China. Focusing on north-facing bedrooms, applying PCMs reduced the duration of overheating in non-air-conditioned buildings in severe cold regions of China by 136 h (Yichun), 340 h (Harbin), 356 h (Shenyang), and 153 h (Dalian). In terms of cooling energy consumption, the energy saved by applying PCMs ranged from 1.48 to 13.83 kWh/m². These results emphasize that the performance of PCM varies with climate change, with the most significant energy-saving effects observed in severe cold regions. In north-facing bedrooms in Harbin, the energy-saving rate was as high as 60.30%. Based on these results, the study offers guidance and recommendations for feasible passive energy-saving strategies for buildings in severe cold and cold regions of China in the face of climate change. Additionally, it provides practical guidance for applying PCMs in different climatic zones in China.

Background: Educational spaces, which represent a vital setting for students’ learning activities, significantly influence both learning efficiency and physiological health. As university teaching spaces are characterised by high occupancy density and prolonged occupancy, it is vital to address the problem of elevated CO₂ concentrations in these spaces. Although effective ventilation design can improve indoor air quality, the relatively short ventilation periods in cold regions of China, driven by winter insulation requirements, often lead to substandard indoor air quality. Purpose: Based on predicted mean vote (PMV), this study explored the effect of natural ventilation on indoor CO₂ concentration during the transition season in cold regions and proposed reasonable optimization strategies. Method: Through the method of combination of measurement and simulation, an effective design method of doors and Windows and an intermittent ventilation strategy for improving the indoor environment quality of teaching space in universities in cold regions of China are put forward. Result: The results revealed that indoor CO₂ concentrations exceeded the standard limit of 1000 ppm for the majority of the periods studied. Peak indoor CO₂ concentrations reached 1970 ppm, 2751 ppm, and 3200 ppm in large-, medium-, and small-sized classrooms, respectively. The duration of exceeding CO₂ concentration accounted for the highest proportion of class time, which were 89%, 93%, and 88%, respectively. Furthermore, optimisation of door and window design and ventilation methods was carried out for a representative medium-sized classroom. The simulation results indicated that while maintaining indoor comfort (−0.5 < PMV < 0.5), peak indoor CO₂ concentrations during class periods decreased from 2551 ppm to 1149 ppm, and the proportion of time for which CO₂ concentrations exceeded standards decreased from 87% to 47%. Conclusions: This study suggests that relevant codes and standards should be refined for the relationship between indoor CO₂ concentration and thermal comfort, and that designers should provide suggestions for suitable door and window design and ventilation strategies to improve indoor air quality in educational spaces in cold regions of China.