Wood chips or particles as well as shredded straw offer desired thermal insulation qualities. When exposed to a humid environment, however, fungal growth on wood and straw is an important consideration. An experimental investigation was conducted in order to evaluate the effectiveness of a simple treatment in mitigating fungal growth on wood- and straw-based insulation. This treatment involved blending of wood chips or particles, or shredded straw with an aerated slurry which offers the potential to mitigate fungal growth on biomass by a combination of physical and chemical effects without imposing a weight penalty. Experimental results verified the effectiveness of this treatment in controlling fungal growth on wood and straw subjected to different moisture conditions.