Mould growth on wood is often a precursor of further decay. Current predictive mould growth models used in building science are based on laboratory experiments, in which the material sample is in hygrothermal equilibrium with ambient air. However, such condition is rarely satisfied in real life building structures and thus these models often fail. The main objective of this project is to deepen the understanding of fungal growth on wood exposed to changing boundary conditions. The focus will be on the hygrothermal interactions amongst the surface layer of the wood substrate, the fungi occupying the surface and the air boundary layer. These interactions will be studied by carrying out both laboratory and computational experiments including the characterization of the hygrothermal properties of material samples, their hygrothermal response and their susceptibility to fungal growth under changing boundary conditions. The outputs of the project will help refining the current mathematical models for mould growth on wood.