Wood is susceptible to fungal attack and over time the structural integrity can be compromised. This risk is of course strongly related to moisture dynamics, as moisture is needed for fungal growth. While existing methodologies, such as lab and field tests, provide valuable insights into wood decay, they often fall short in replicating real-life conditions, particularly within the intricacies of the building envelope. To address this limitation, a set-up is needed in which we can test a building envelope in different moisture conditions, mimicking as close as possible real-life situations. Moreover, by employing advanced tools like X-ray CT scanning and heat-air-moisture simulations, we can get a better understanding of the risk of wood decay in the building envelope and how it is perceived in state-of-the-art simulation tools used in architecture to study the physics of the building envelope. In this paper, we further build on the concept of the Fungal Control Unit, short FCU, which we first presented in 2008. The current concept is a small and simplified version of a hot box - cold box set-up, consisting of two climatic chambers to reproduce exterior climate and interior conditions. Our FCU allows us to generate very wet and warm conditions at one side and cold and dry conditions at the other side of a wall element, as such generating a moisture gradient across the building envelope. These conditions are often predicted to result in increased water content and mould growth in HAM simulations, and the FCU set-up allows us to test these simulations. In this paper, we show the potential use of the FCU set-up based on two examples. First, a wall set-up with vapour-open and vapour-tight wood boards, exposed in the FCU for 9 months without any visual signs of decay. Second, we show first results of X-ray CT scanning and HAM simulations from an ongoing experiment for visualizing and simulating progress of moisture inside smaller wall elements, with different (bio-based) insulation materials. In conclusion, the FCU set-up in combination with X-ray CT and HAM, allow us to mimic real-world conditions and visualize and simulate the intricate processes, providing a comprehensive understanding crucial for ensuring the longevity of wooden structures in authentic building scenarios, as we seek even more sustainable construction practices in the future.

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