Reviewed by Lexie CornerJan 13 2025
Researchers at ETH Zurich have developed a climate-friendly wall and ceiling covering that temporarily retains moisture, helping to maintain a comfortable indoor environment in heavily occupied spaces. According to a study published in Nature Communications, the covering components are manufactured using 3D printing and are composed of mineral waste materials.
A team of researchers at ETH Zurich has developed a new, moisture-binding material. If this component is used in walls and ceilings, it reduces the humidity indoors. Image Credit: Pietro Odaglia / Josef Kuster
Whether in a government office waiting area, a museum exhibition space, or a meeting room in an office building, densely occupied spaces often experience rapid increases in humidity, contributing to discomfort.
Ventilation systems are commonly used in office and administrative buildings to dehumidify spaces and maintain a comfortable environment. While mechanical dehumidification is reliable, it is energy-intensive and, depending on the amount of power used, has an adverse effect on the climate.
To address this, researchers at ETH Zurich investigated a novel approach for passively dehumidifying interior spaces. In this context, "passive" refers to temporarily storing excess humidity within walls and ceilings.
Instead of relying on mechanical systems to remove moisture, the approach utilizes a hygroscopic, moisture-binding material that temporarily absorbs humidity. The stored moisture is then released when the space is ventilated naturally, reducing energy consumption and environmental impact.
Our solution is suitable for high-traffic spaces for which the ventilation systems already in place are insufficient.
Guillaume Habert, Professor and Supervisor, Sustainable Construction, ETH Zurich
Waste Material from Marble Quarrying
Habert and his research team followed the principle of the circular economy to identify a suitable hygroscopic material. They used finely ground waste from marble quarries as the primary material. A binder was required to transform this powder into moisture-resistant wall and ceiling components. This was achieved using a geopolymer, a material composed of metakaolin (a byproduct of porcelain production) and an alkaline solution made of potassium silicate and water.
The alkaline solution activates the metakaolin, creating a geopolymer binder that bonds the marble powder into a solid material. This binder functions similarly to cement but generates significantly less CO2 during production.
The team produced a prototype wall and ceiling component measuring 20 x 20 cm with a thickness of 4 cm. Production was performed using 3D printing under the direction of Benjamin Dillenburger, Professor of Digital Building Technologies. The process, known as binder jet printing, involves layering the marble powder and binding it with the geopolymer solution.
This process enables the efficient production of components in a wide variety of shapes.
Benjamin Dillenburger, Professor, Digital Building Technologies, ETH Zurich
Moisture-Controlling Components Increase Comfort
The use of geopolymer and 3D printing to create moisture reservoirs represents an innovative approach to sustainable construction. Magda Posani, a building physicist, initially investigated the material’s hygroscopic properties at ETH Zurich before joining Aalto University in Espoo, Finland, as a professor.
The concept stems from Vera Voney’s Ph.D. thesis, supervised by Senior Research Associate Coralie Brumaud and architect Pietro Odaglia, who contributed to the development of both the material and the 3D printing equipment at ETH.
We were able to demonstrate with numerical simulations that the building components can significantly reduce humidity in heavily used indoor spaces.
Magda Posani, Building Physicist and Professor, Aalto University
For the study, it was assumed that hygroscopic elements were installed on the walls and ceiling of a reading room in a public library in Oporto, Portugal, accommodating 15 people. Over the course of a year, Posani simulated how often and to what extent the relative humidity in this virtual room exceeded the comfort range of 40–60 %.
Based on the simulations, Posani calculated a discomfort index, quantifying the impact of high or low humidity on comfort levels. The results indicated that, compared to conventional painted walls, the discomfort index could be reduced by 75 % with the use of moisture-binding materials. Increasing the component thickness from 4 cm to 5 cm further reduced the discomfort index by up to 85 %.
More Climate-Friendly than Ventilation Systems
The hygroscopic wall and ceiling components are environmentally advantageous, emitting significantly less greenhouse gases over a 30-year life cycle compared to a ventilation system designed to achieve equivalent dehumidification. In simulation calculations, these components were also compared to clay plaster, a traditional material used for passive humidity regulation in indoor environments. While the clay plaster demonstrated even lower greenhouse gas emissions, its capacity to store water vapor was notably reduced.
ETH researchers demonstrated that a combination of geopolymer and 3D printing can produce wall and ceiling components capable of effective moisture buffering. With this proof of concept established, the technology is now ready for further development and scaling toward industrial production.
Research efforts are ongoing. In collaboration with Turin Polytechnic and Aalto University, ETH Zurich is working on optimizing wall and ceiling components to achieve even lower greenhouse gas emissions. One thing is certain: if Switzerland is to meet its net zero aim by 2050, it requires buildings that emit as little greenhouse gases as possible during construction and operation.
Journal Reference:
Posani, M., et al. (2025) Low-carbon indoor humidity regulation via 3D-printed superhygroscopic building components. Nature Communications.doi.org/10.1038/s41467-024-54944-1