Energy-saving and overheating-mitigation effects of phase change materials on buildings in cold regions

Climate change has intensified indoor overheating in residential buildings during summer in cold regions of China, increasing the demand for cooling energy. However, current building design standards focus mainly on winter insulation, with limited consideration for summer heat protection. This study evaluates the effectiveness of incorporating phase change materials (PCMs) into building envelopes to achieve year-round energy savings. Indoor temperature monitoring was conducted in nine rooms across five representative cold-region cities during summer 2023, revealing 451 to 1785 h of overheating (temperature >26 °C). Two experimental cells were built in Harbin, and measurements showed that using PCMs reduced indoor temperature fluctuations by 6.03 °C. Simulation models, calibrated using experimental data, were used to assess annual energy performance in typical south bedrooms, north bedrooms, and living rooms in the five cities. Results indicated that PCMs reduced cooling energy consumption by 1.75–3.30 kWh/m² and heating energy consumption by 4.49–14.77 kWh/m² in south bedrooms. Additionally, Simulation results further indicated that after applying PCMs, the static overheating duration in Yichun (1A), Harbin (1B), Changchun (1C), Dalian (2A), and Beijing (2B) decreased by 5.81 %, 2.25 %, 4.50 %, 5.16 %, and 2.25 %, respectively. These findings demonstrate that PCM-enhanced envelopes can improve thermal comfort and reduce energy use in both summer and winter. The study highlights the need to revise building codes in cold regions of China to include summer heat mitigation strategies and provides practical data to support the implementation of PCMs in residential design.