While additive manufacturing has fundamentally advanced the fabrication of structural elements, the functional potential of 3D-printed interior coatings for passive climate regulation remains a critical knowledge gap. Specifically, the correlation between the distinct microstructural anisotropy induced by extrusion-based printing and dynamic hygrothermal response of mortars remains poorly understood. This study assesses the hygrothermal performance of low-embodied-energy clay- and air lime-based mortar samples produced via 3D printing. The influence of the partial binder substitution with gypsum, as well as the effect of a painting system, is also investigated. A comprehensive experimental campaign assessed water vapor permeability, sorption isotherms, and Moisture Buffering Value, correlating these hygric properties with microstructural characterization using Mercury Intrusion Porosimetry and Scanning Electron Microscopy. Results indicate that extrusion-based manufacturing preserves a distinct inter-filament porosity, resulting in hygroscopic performance comparable to, and in specific clay matrices superior to, that of traditionally cast mortars. The 3D-printed clay- and lime-based mortars exhibited a moderate increase in moisture buffering capacity, validating the potential of these eco-efficient indoor coating systems as passive humidity regulators for the built environment. Moreover, the painting system demonstrates only a slight influence on the moisture capacity of the samples, highlighting the dominant role of the microstructure.
Rocha et al. (Tue,) studied this question.