A novel solar-active integrated biobased façade system for enhanced thermal storage, energy efficiency, and climate adaptability

• Combination of passive house thermal mass with active solar energy technology. • Closed-loop system moderates orientation-driven loads, improving thermal uniformity. • Modular numerical models enable rapid modeling and simulation. • Comparison of various control strategies for energy savings and thermal comfort. • The system delivered 21.0–22.4 % energy savings in cold climates across control strategies. By integrating solar energy technologies into thermally activated building systems and employing renewable energy as the primary source, buildings can achieve significant enhancements in thermal storage capacity, energy efficiency, and indoor thermal comfort. This study introduces a solar-active integrated biobased façade system, which harnesses solar radiation on the south-facing façade and transfers the captured heat via embedded piping to a thermal storage module located on the north façade, thereby supplying indoor heating. Compared to conventional biobased envelope systems and standard thermally activated building systems, the proposed structure not only balances façade thermal gradients between south and north sides but also incorporates a thermal storage mechanism to mitigate solar energy intermittency, thereby expanding the practical applicability of renewables in the built environment. Experimental results demonstrated that the proposed structure increased indoor temperatures by an average of 12.7 ℃ while achieving a solar energy utilization rate of 77.9 %. To support practical deployment, a modular design framework and case-based numerical simulations were developed. These analyses revealed that operating the circulation pump at 0.1 MPa and implementing an irradiance-based delay control reduced energy use by 26.6 %, which further improved to 31.7 % with the integration of phase change materials. Additionally, cold-season simulations across four representative cities showed that the proposed structure achieved 21.0–22.4 % energy savings in cold regions, and in severe cold climates, it reduced energy demand by 9.1 % and decreased discomfort hours by 85.4 %. These results, while validating that the proposed structure effectively provides heating, also offer multidimensional design recommendations for similar systems.