Analyses of the building insulation performance of double-layer walls with a phase change material in the hot summer and cold winter region

This article studies the temperature regulation requirements of buildings in the hot summer and cold winter (HSCW) region through a combination of experiments and numerical simulations. The bidirectional heat transfer process in phase change material (PCM) walls was visualized using heatlines, and the thermal transfer behaviour characteristics between PCM walls and conventional walls were compared and analysed. The findings showed that double-layer PCM walls could effectively regulate energy, including reducing the peak temperature of the interior surface by 0.9–1.2°C in summer and increasing its minimum temperature by 0.8–1.7°C in winter, while the average interior temperatures for east, south, west and north-facing walls could be increased by 0°C, 1°C, 0.7°C and 0.5°C, respectively. Energy consumption analyses revealed that the optimal phase change temperatures for double-layer PCM walls in Changsha's climate are 23°C and 18°C. A PCM layer that is 30 mm thick could result in the biggest energy savings, lowering cold and hot loads by 39.3% and 23.1%, respectively. With a payback period ranging from 3.9 to 5.2 years, double-layer PCM walls have a high potential for widespread adoption across the 11 cities in the HSCW region. This study provides experimental support and recommendations for PCM wall design optimization in challenging climates.