Energy, exergy and economic analysis of PCM applied in multilayer wall under different climatic regions of France

• A parametric study evaluates PCM-integrated walls across four distinct climates. • Energy, exergy, and economic indicators reveal non-equivalent performance trends. • PCM thickness requires a balance between energy saving and economic return. • Exergy performance varies strongly with climate and differs from energy results. • Optimal PCM peak melting temperature is specific rather than universal. The increasing energy demand of the building sector, together with climate change mitigation and energy transition requirements, highlights the need for effective energy management strategies. Phase change materials (PCMs) integrated into building envelopes, particularly multilayer wall systems, have shown strong potential for reducing cooling related heat gain and improving thermal regulation. However, the performance of PCM-integrated multilayer walls has largely been evaluated from an energy perspective, with limited attention to thermodynamic efficiency and economic viability. In this study, the energy, exergy, and economic performance of a sustainable bio-based PCM integrated into multilayer wall systems is systematically evaluated under four representative French climates. A full factorial analysis is conducted to examine the effects of PCM thickness, melting temperature, and placement within the wall. The results show that PCM thickness is the dominant parameter affecting thermal performance, whereas the preferred configuration varies with climate and decision priority. No single configuration simultaneously optimizes energy saving, exergy efficiency, and economic return. However, the balanced configuration remains the same across all four cities, corresponding to a PCM thickness of 5 cm, a peak melting temperature of 28 °C, and placement at the brick–plaster interface. Overall, the study provides climate sensitive design guidance and highlights the importance of multi-criteria evaluation for PCM wall design.