Biobased building materials: Moisture characteristics and fungal susceptibility.

• Each biobased building materials has its own specific moisture characteristics. • All biobased materials are very vulnerable to seeping liquid water. • Wood chip board was mouldy after 6 days. • Fungal growth can be avoided if the material can dry out within 3–5 days. • Stachybotrys chartarum was found on both hemp fibre insulation and hempcrete. Climate changes make water damages and humidity problems more frequent and more severe. To combat this, inorganic building materials must be substituted by biobased materials. However, biobased materials are expected to be more susceptible to moisture and fungal growth than inorganic materials. The purpose was to stress test 14 biobased materials using three worst-case scenarios: 1) flooding, 2) leaking water pipe and 3) prolonged high humidity. The results of the stress tests showed that all 14 materials behaved differently, even materials made from the same raw material. Results showed that most materials dried out quickly after the flooding experiment, while some dissolved (clay render), lost structural integrity and became mouldy (wood fibre insulation). Results also showed that some materials (wood fibre insulation) absorbed large amounts of moisture during the high humidity experiment without becoming mouldy, while others lost structural integrity (hemp fibre insulation) or became mouldy after a month (wood chip board). When simulating leaking pipes, the results showed that some materials (wood chip board, grass-, hemp- and wood fibre insulations) went mouldy after a week, while others stayed mould free for three months. Aspergillus versicolor, A. westerdijkiae, A. niger, Chaetomium globosum and Trichoderma viride were found on most materials except hemp fibre insulation and hempcrete, while Stachybotrys chartarum was only found on hemp materials. Most materials showed good moisture buffer properties but were vulnerable to liquid water. Therefore, great care must be taken when selecting biobased materials for constructions that are at risk of water damage.