Durability assessment of alkyl ketene dimer hydrophobic treatment of bio-based thermal insulation materials

• Provide insight into the durability and suitability of mycelium and grass bio-based composites as green and sustainable insulation materials. • Eco-friendly and cost-effective AKD as a hydrophobic modification to effectively reduce hygric properties and improve thermal insulation capacity. • Both mycelium and grass bio-based composites with AKD modification significantly improved their resistance ability to mould growth. • Preferentially recommended using AKD-modified grass in distinct climates when applied as insulation components in assembly walls. • Providing the feasible guidance of accelerating bio-based composite practical application on insulation materials of sustainable building construction. Bio-based composites are increasingly used as thermal insulation materials in construction due to sustainability and low thermal conductivity. However, their high moisture absorption can negatively affect performance and mould growth risk, shortening product lifespan. This study introduces alkyl ketene dimer (AKD) as an eco-friendly and economical solution for the hydrophobic treatment of two bio-based composites, mycelium and grass, to enhance their durability. We compare the physicochemical properties, hygrothermal performance, and mould growth resistance of bio-based composites before and after hydrophobic modification while evaluating their durability in simulated building envelopes across different climates. Results showed that the modified bio-based composites were well-grafted with AKD. The water absorption of bio-based composites significantly decreased after modification, and the mould growth resistance capacity of modified composites was significantly improved. Moreover, hygrothermal simulations reveal that AKD modification effectively enhances their suitability under different climate profiles, particularly when modified grass composites are applied.