Indoor humidity significantly impacts our comfort, health, and well-being, influencing factors such as sleep quality, productivity, and overall indoor living conditions. The optimal range for indoor relative humidity is widely considered to be 40–60%, as it helps prevent health issues like respiratory irritation and joint pain while limiting the spread of mould, bacteria, and airborne viruses, including influenza and SARS-CoV-2. However, current approaches to managing indoor humidity often rely on energy-intensive mechanical systems, which increase buildings' carbon footprints. An alternative approach that could prove useful in several situations rely on the use of low-carbon, highly hygroscopic 3D-printed building components to reduce dependence on mechanical systems for humidity regulation.

In this work, we consider 3D-printed building with high moisture buffering ability, designed as finishing panels for interior walls and ceilings. The first type, developed at ETH Zurich, utilises a superhygroscopic geopolymer-based composite and a gyroid-inspired geometry. The second type, created at Politecnico di Torino, employs a highly hygroscopic clay-based composite and a layered geometry, achieved by overlapping extruded material in varying paths. These geometries enable a much higher surface area-to-volume ratio compared to solid components. This feature not only reduces material usage, leading to lower weight and embodied emissions, but also enhances the panels’ moisture-buffering capacity. Experimental results are presented and techniques for modelling the moisture-buffering performance of these complex 3D-printed geometries is explored. The numerical simulations rely on conventional dynamic hygrothermal simulation tools, such as those in the WUFI software family. The simulations are validated against laboratory measurements.

The novelty of this work lies in proposing methodologies to accurately simulate the hygroscopic behaviour of 3D-printed components with complex geometries. As 3D printing gains popularity for producing high surface area components suited to moisture buffering, the need for accurate modelling tools becomes increasingly critical. This work addresses the current gap in the ability to simulate such components with standard hygrothermal tools, which are primarily designed to simulate the hygrothermal behaviour of flat, full-volume elements.

Hygrothermal calculation tools are frequently used in the moisture safety design process in order to predict future conditions in the building envelope. In general, the results from calculations vary depending on the quality of the input data and on the different input parameters. Sensitivity analysis is often carried out by changing one single parameter at a time or only investigating dependencies in certain quantities. Introducing real measurements with sensors’ errors, any comparison to calculation is difficult as the response may include random effects. This study aims to develop and exemplify a method to identify and evaluate the impact of various parameters on calculated temperature, relative humidity and moisture content in building components over time. To ensure that hygrothermal calculation models provide reliable and useful results, it is important to use appropriate performance metrics. These metrics could quantify the differences between calculated and measured values and provide insight into the hygrothermal calculation model's accuracy. Common performance metrics include a selection from overall statistical measures such as mean difference, root mean square error and correlation coefficient. In many cases, even a direct graphical comparison of measured and calculated values may be sufficient to rank results. However, as more refined models are derived in combination with more available measurement data, better methods need to be developed. A method was invented using an analytical performance metric function that ranks the difference in output data with respect to time shift effects, outliers, RMS-values and by applying a frequency weighing filter to the residuals. The relationship between temperature, humidity and moisture content has been respected by using different sensitivity threshold values for different quantities in the method. Using long-term measurement data from real occupied houses, the invented method can identify important parameters and factors to improve proper hygrothermal calculations.

In cavity walls and other masonry systems, the material interfaces—such as brick-mortar or brick-airgap—play a crucial role in hygrothermal performance. Variations in mortar properties and the presence of air gaps can substantially influence moisture and heat transport, affecting the structure's durability and thermal efficiency over time. This research explores the combined effects of material characteristics and construction details on the hygrothermal performance of traditional Chinese cavity walls using advanced 2D simulations. The findings indicate that mortar with higher liquid conductivity than brick increases the risk of frost damage at the interface, while airgap geometry significantly affects vapor diffusion and subsequent bio-deterioration at the brick-air interface in non-vented air gaps. Additionally, this research evaluates how simplified 1D simulations may underestimate practical risks, such as localized moisture accumulation and thermal bridging, highlighting the necessity of more detailed 2D modeling for accurate risk assessment. These insights contribute to optimizing construction practices and enhancing the long-term durability and efficiency of masonry structures.

A major challenge in the field of Building Physics is using the right set of weather data sets that represent future weather conditions while decrease the number and length of simulations. In this work, multiple approaches for synthesizing weather files are implemented to generate typical and extreme future weather data sets. Results are being compared with long-term simulations, investigating the performance of each representative weather data set in predicting the performance of a typical wooden frame wall construction. Results show the capability of each approach for estimating the moisture conditions in wall layers and probable risks.

As global warming increases the demand for active cooling methods grows, especially in urban areas. Existing floor heating infrastructure is used increasingly for space cooling purposes in residential buildings. This results in noticeably lower temperatures and may lead to higher humidity in the flooring area with increased moisture content in floor coverings. Due to that, new risks concerning deformation, delamination and mould growth for wood flooring occurs.

In this work, the present and future impact of floor cooling on the hygrothermal behaviour of wooden parquets was analysed based on an extensive hygrothermal simulation study representing 2423 different parameter constellations using a sequence of different FE simulation tools. Therefore, different indoor climates, assuming different building alignments, apartment situations and outdoor climate scenarios, were simulated using DesignBuilder®. Subsequently these indoor conditions were set as boundary conditions in a hygrothermal paramter study of different flooring components in WUFI Pro®.

Results show that inlet temperatures of cooling systems must be adapted considering apartment alignment, orientation, position, thermal conductivity and water vapour diffusion resistance of the flooring to avoid critical moisture contents leading to mould growth and high deformation.

The gradual reduction in the energy demand of buildings has resulted in increasing requirements for building insulation. In the past, many buildings were additionally insulated with external thermal insulation component systems (ETICS). However, these structures no longer meet current requirements, and they require further renovation in the near future.

One such option is to a add new ETICS system with additional insulation to an existing ETICS system. The present paper constitutes a case study that explores the implications of such a modification to the existing system in a Central European region, with a particular focus on the changes in moisture regime of insulated walls and their potential impact on materials. The study is based on HAM modelling. This study also explores the evolution of the climatic load on structures in the context of global climate change, as outlined in the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change. Meteorological data considering different climate change scenarios have been employed in HAM simulations. The objective is to ascertain how the aforementioned changes in the Central European region will affect the climate loads of building structures of a given type.