Impact of Biodeterioration on the Structural and Thermal Insulation Properties of Plant Fibre-Reinforced Polymer Biocomposites for Construction Applications

Natural fibre-reinforced polymer biocomposites are increasingly considered for construction applications because of their renewable reinforcement, low density and potentially reduced environmental impact. Their durability, however, is strongly constrained by moisture, which promotes fibre swelling, weakens the fibre–matrix interphase and creates conditions favourable to fungal colonisation. This review examines the effects of moisture and biodeterioration on the structural and thermal performance of natural fibre-reinforced polymer composites used in construction. Across the reviewed studies, moisture and hygrothermal ageing produced tensile-strength reductions ranging from less than 10% to approximately 40%, while losses in stiffness or impact performance exceeded 40–70% in particularly susceptible systems. In contrast, directly comparable quantitative data linking fungal biodeterioration with changes in thermal conductivity remain scarce, representing a major research gap. Current durability standards, particularly ISO 846:2019, provide useful screening data but do not fully reproduce the cyclic hygrothermal conditions experienced by porous, hygroscopic construction biocomposites. More reliable durability assessment requires integrated microbiological, hygrothermal, mechanical and microstructural testing supported by advanced non-destructive diagnostics. Protection strategies should combine moisture control and biological resistance while considering long-term service performance, environmental impacts, recyclability and end-of-life constraints.