Mycelium–coir-based composites for sustainable building insulation

Abstract

Building insulation materials are widely used in building envelopes to improve the energy efficiency of buildings and effectively reduce the energy cost for space cooling and heating. As a result, they contribute to a sixth of the world's total energy consumption and GHG emissions. However, many conventional insulation materials are either energy-intensive or made of petroleum-based plastics, and their production is not sustainable. Here, we focus on fungal biotechnology to produce mycelium–coir-based composites (MCBCs) that are fully derived from biomass with potential application in insulating building envelopes. We inoculated mycelium from simple spores to an integrated network with coir fibers in the form of boards and blocks. MCBCs were found to be good insulators with low thermal conductivity (0.035 ± 0.008 W m⁻¹ K⁻¹), similar to polymer foams. We isolated the thin surface film of pure mycelium and measured the thermal conductivity with a laser flash method. An ultralow thermal conductivity of 0.015 ± 0.003 W m⁻¹ K⁻¹ was identified for Ganoderma lucidum, which was lower than the thermal conductivity of pure air, making the film essential for MCBC insulation. Moreover, our series of in-lab tests demonstrated that the composite was more fire-tolerant and hydrophobic than conventional insulation materials, had load-bearing capability similar to polymer foams in compression, and could be further densified to reach optimal specific mechanical functions according to data-driven models. Our study demonstrates that MCBCs are promising materials that may be used to reliably and sustainably improve building insulation functions.