When exposed to conditions favourable for decay, bio-based building materials can be susceptible to degradation. Their ability to withstand deterioration over time (performance) depends on the intrinsic or enhanced durability of the material as well as its wetting and drying behaviour. The effect of fungicidal components in wood is known since long. Other material characteristics, such as the material’s moisture dynamics and structure, are crucial as well in prolonging a material’s service life in outdoor exposure conditions. The importance of these other material characteristics should not be underestimated, as there are many opportunities to alter a material’s moisture dynamics and to optimize the structural design of engineered wood products and bio-based insulation products. In order to do so, it is necessary to understand how different material characteristics influence the performance. In this paper, we assess the moisture dynamics of oriented strand board (OSB), porous bituminized wood fibre board (PBF), radiata pine plywood (PL), thermally modified spruce (TMT) and two wood fibre insulation boards (WF-A and WF-B). With the ‘paste test’, we assess whether these materials contain fungicidal components affecting decay. Additionally, we assess how they perform in an adapted mini-block test. We are able to show that fungicidal components are not always of major importance for the durability of a bio-based building material. Some of the assessed materials have a remarkable moisture performance. We need to work towards specific moisture performance criteria and consider including them in performance classification.

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