Thermal Performance and Energy Efficiency Evaluation of Thermally Activated Composite Panel for Retrofitted Buildings Across Diverse Climate Zones of Gansu, China

This study investigates the use of thermally activated composite panels (TACP) as an energy-efficient retrofitting solution for existing buildings. By utilizing low-grade heat sources, TACP offers significant energy efficiency and carbon emission reduction. To address the challenges posed by high embodied carbon, exterior envelope delamination, and fire safety risks associated with conventional insulation materials, three TACP configurations were proposed: external insulation with externally embedded pipes (EE-TACP), external insulation with internally embedded pipes (EI-TACP), and internal insulation with internally embedded pipes (II-TACP). These were proposed for adapting TACP-walls to the diverse climate zones of Gansu Province. To clarify the thermal performance, energy-saving potential, and reduction effect on conventional insulation thickness of TACP-walls under different climatic conditions and heat source temperatures, dynamic heat transfer models of the TACP-wall were developed and validated. Three energy-saving rate (ε) indicators were introduced to analyze the dynamic thermal behavior in typical cities across the three climate zones of Gansu Province. A comparison was made among the three configurations in terms of instantaneous thermal response characteristics, cumulative internal surface heat load, and ε, relative to both non-insulated walls (NI-walls) and conventional insulated energy-saving walls (CE-walls). The results demonstrate that the application of TACP-walls significantly enhances thermal performance under all three climatic conditions. Irrespective of operating conditions, the ε remains essentially constant corresponding to the four insulation thicknesses, indicating that traditional thickness can be drastically curtailed. EE-TACP, EI-TACP, and II-TACP achieve pronounced ε values of 7.57/7.97/7.50 relative to NI-wall and CE-wall at inlet temperatures of 28–36 °C. Among the three configurations, EI-TACP performs most prominently across all climate zones. The findings provide a valuable reference for the application and optimization of thermally activated technology in energy-efficient retrofits of existing buildings.