High-performance phase change material-integrated systems for summer climate optimization

Energy retrofitting and the conversion of existing buildings into dwellings are key strategies for reducing decarbonisation in the building sector and mitigating climate change. Established energy efficiency measures, such as thermal insulation, airtightness and heat recovery, have proven effective in reducing heating demand. However, as the performance of buildings improves with these approaches, they increasingly influence the overall energy balance, particularly under warm conditions. In this context, the integration of phase change materials (PCMs) into building envelope components is a promising strategy for enhancing latent thermal energy storage (LTES) and improving indoor thermal comfort in both renovations and new constructions scanarios. This study investigates the performance of an innovative integrated PCM component based on LTES principles, aimed at improving the summer performance of buildings. The proposed system consists of a 30 mm thick panel composed of paraffinic PCM impregnated in a highly porous matrix operating in synergy with a night ventilation cooling strategy. The experimental campaign was conducted on two identical test cells where the composite PCM panel was integrated into the roof of one test cell and compared to the reference without PCM. Results show that the PCM system achieved a total heat gain reduction of 23% and a 55% average decrease in peak heat flux compared with the reference configuration. The internal surface temperature decreased by up to 4.5 °C, while the operative temperature reduction reached 1.8 °C, confirming a significant improvement in indoor comfort. The observed time-lag icreased between 1 h 45 min and 17 h, demonstrating the effective thermal buffering capacity of the PCM layer. Overall, these results confirm that the application of LTES panels, combined with night ventilation strategies, effectively shifts peak loads, improves indoor thermal comfort, and reduces dependence on active air conditioning systems. The versatility of the design allows for its effective use in both existing buildings with space constraints and new constructions, contributing significantly to the optimisation of energy efficiency and the thermal comfort of the indoor spaces.