Indoor humidity significantly affects building occupants’ comfort, health, and well-being. Ideally, indoor relative humidity levels should stay within 40–60% to prevent respiratory irritation and the spread of mould and viruses. Conventionally, HVAC systems are used for indoor humidity control, but they have considerable environmental impact due to both the embodied emissions in the machinery and emissions during their operation. This study explores an alternative approach using low-carbon, hygroscopic, 3D-printed panels that regulate indoor humidity passively. Two types of panels are considered: one developed by ETH Zurich using a superhygroscopic geopolymer composite with a gyroid-based geometry, and the other designed by Politecnico di Torino using a hygroscopic clay composite with a multi-layered geometry. These designs enhance moisture buffering by exposing a large surface area of the materials to indoor air. Experimental results and tentative modelling approaches are discussed, comparing simulations with measured outcomes. This work highlights the need for accurate modelling strategies for representing the hygroscopic behaviour of 3D-printed components with complex geometries, using conventional dynamic hygrothermal simulation tools.