Microstructure-Driven Hygrothermal Behavior of Mycelium-Based Composites for Bio-Based Insulation

Sina Motamedi, Daniel R. Rousse () and Geoffrey Promis
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Sina Motamedi: Research Group in Energy Technologies and Energy Efficiency (t3e), École de Technologie Supérieure (ÉTS), Université du Québec, Montreal, QC H3C 1K3, Canada
Daniel R. Rousse: Research Group in Energy Technologies and Energy Efficiency (t3e), École de Technologie Supérieure (ÉTS), Université du Québec, Montreal, QC H3C 1K3, Canada
Geoffrey Promis: University of Picardie Jules Verne, Innovative Technologies Laboratory (LTI), 80025 Amiens Cedex, France

Energies, 2025, vol. 18, issue 11, 1-25

Abstract: This study investigates the coupled hygrothermal behavior of mycelium-based composites (MBCs) as a function of their microstructural organization, governed by fungal species, substrate type, additive incorporation, and treatment method. Eleven composite formulations were selected and characterized using a multi-scale experimental approach, combining scanning electron microscopy, dynamic vapor sorption, vapor permeability tests, capillary uptake measurements, and transient thermal conductivity analysis. SEM analysis revealed that Ganoderma lucidum forms dense and interconnected hyphal networks, whereas Trametes versicolor generates looser, localized structures. These morphological differences directly influence water vapor transport and heat conduction. Additive-enriched composites exhibited up to 21.8% higher moisture uptake at 90% RH, while straw-based composites demonstrated higher capillary uptake and free water saturation (up to 704 kg/m 3 ), indicating enhanced moisture sensitivity. In contrast, hemp-based formulations with Ganoderma lucidum showed reduced sorption and vapor permeability due to limited pore interconnectivity. Thermal conductivity varied nonlinearly with temperature and moisture content. Fitting the experimental data with an exponential model revealed a moisture sensitivity coefficient thirty times lower for GHOP compared to VHOP, highlighting the stabilizing effect of a compact microstructure. The distinction between total and effective porosity emerged as a key factor in explaining discrepancies between apparent and functional moisture behavior. These findings demonstrate that hygric and thermal properties in MBCs are governed not by porosity alone, but by the geometry and connectivity of the internal fungal network. Optimizing these structural features enables fine control overheat and mass transfer, laying the groundwork for the development of high-performance, bio-based insulation materials.

Keywords: bio-based building materials; fungal insulation materials; hygrothermal behavior modeling; vapor permeability in mycelium-based insulation; thermal conductivity of porous materials; GAB sorption model; scanning electron microscopy (SEM) in bio-composites; Ganoderma lucidum vs. Trametes versicolor (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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