Investigation of Energy Conservation in Classic Buildings with PCM Multi-Layer Walls

Integrating Phase Change Materials (PCMs) into building envelopes presents a viable strategy for enhancing energy efficiency, stabilising indoor temperatures, and reducing carbon emissions, particularly in historical and modern structures. This study explores the effectiveness of PCM integration in various building types, including Victorian-era and hospital buildings in cold climates and modern office buildings with double-glazed windows. The primary aim was to investigate how PCM could reduce heating and cooling demands, contributing to global sustainability goals such as the European Union’s climate-neutral strategy by 2050. Prototypes replicating the wall structures of these buildings were constructed for an experimental investigation, and PCM of RT28HC, with a melting point of 27°C, was integrated into the walls. Through a combination of experimental testing and dynamic simulations conducted using TRNSYS, the study identified that the optimal PCM placement within these walls occurred between 341 mm and 356 mm from the external wall surface. This positioning allowed the PCM to fully activate at its phase change temperature, reducing heat transfer and maintaining stable internal wall surface temperatures. In modern office buildings with double-glazed windows, this configuration resulted in 34% to 37% savings in heating and cooling energy consumption while maintaining a Predicted Mean Vote (PMV) of 0.21 and a Predicted Percentage of Dissatisfied (PPD) of 6.0%, ensuring optimal thermal comfort for occupants. In Victorian-era hospital buildings with thick multi-layered walls, placing the PCM at the optimal depth led to a 5.3% to 6.2% reduction in energy consumption. The experimental results further indicated that this PCM placement expanded the indoor temperature range by up to 7.9°C and mitigated peak temperature fluctuations by 1.74°C to 2.0°C, significantly improving indoor comfort. However, PCM layers positioned near the outer wall in cold climates often failed to reach the necessary phase change temperatures, reducing their effectiveness. The study also validated a critical model that described heat transfer across multi-layered PCM walls with integrated windows using an exponentially decaying function combined with a sinusoidal component, accurately reflecting the PCM’s phase change behaviour. The comparison between experimental and simulation results confirmed the reliability of the models, with Mean Absolute Percentage Error (MAPE) values below 20% and Root Mean Square Error (RMSE) values ranging from 10.41 to 16.44, indicating high accuracy in predicting PCM performance. These findings have underscored the practical benefits of PCM integration in enhancing energy efficiency, stabilising indoor temperatures, and improving thermal comfort, particularly in heritage buildings and modern office constructions. The validated simulation models have provided a robust framework for optimising PCM placement in building designs, supporting energy conservation and aligning with global environmental targets. Future research should explore long-term PCM performance across different climates and investigate synergies with other sustainable building technologies.