Toward a Digital Design Framework for the Thermal Tunability of 3D Printed Envelopes.

Large-scale extrusion-based additive manufacturing (AM) has emerged as a potential alternative for construction, addressing the challenges associated with the high carbon footprint of the building industry. Although AM enables the creation of intricate design geometries through controlled material deposition, providing innovative solution strategies for design construction, large-scale 3D printed structures are limited to a single homogeneous material, such as cement or clay, and their functionality is restricted to load-bearing formwork. Although still at a nascent stage for building construction, multimaterial additive manufacturing (MMAM) has emerged as a promising technology for the industry to overcome this limitation and reduce the embodied carbon of 3D printed structures by limiting the use of structural materials through topology optimization strategies. MMAM enables the fabrication of functionally graded materials (FGMs) by controlling the extrusion ratio between two or more distinct materials, resulting in building envelopes with multiple performance characteristics and functions. While research has focused on improving the structural performance of 3D-printed envelopes through MMAM, limited attention has been given to optimizing thermal performance and energy efficiency. An increasing interest in thermal energy storage technologies for buildings using the latent heat storage capacity of microencapsulated phase change materials (mPCMs) is related to the advantages of improving energy efficiency using materials that can absorb, store, and release heat when their temperature changes. To this end, this study proposes an FGM design-to-construction methodology for large-scale structures that optimizes the thermal performance of 3D-printed envelopes by locally tuning the distribution of heterogeneous mixes of clay and mPCMs during the AM process. The results of the digital simulations and physical tests show that the local optimization of mPCM and clay within the wall thickness according to the specific temperature differential can provide annual energy reductions compared with a homogeneously printed envelope without embedded mPCM.