Long-term Functionality of a Passive Phase-change Materials Building Application after more than a Decade of Operation

For over two decades, latent heat storage (PCM) systems in building applications have been regarded as a promising technology for preventing overheating in the warm season without increasing cooling energy demand. This study aimed to investigate whether PCM can have a noticeable influence on thermal comfort even after up to 14 years of operation, which has not yet been investigated. For this, we collected PCM material samples in some buildings, which we then examined in the DSC laboratory, and analysed a real building application in southern Germany in detail by collecting measurement data and creating building simulations. The DSC measurements revealed a decrease in performance by 12-26%. However, the simulation results did not show a clear decrease in the performance of the PCM. Instead, they indicated that the paraffin-based PCM still had a positive effect on thermal comfort, reducing room temperatures by a maximum of 1.06 K and in average by 0.34 K during working hours. The PCM also reduced cooling degree hours by 15% during the hot months of July and August. An analysis of the user behaviour showed that there might be potential for improving thermal performance, especially through better use of blinds, windows and night ventilation.