## 3 Results and Discussion
### Characterization of the Mycelium-Based Composites
\begin{tabular}{c} **Capillary** \\ **Absorption,** \\ **Wc** \\ **W\({}^{\mathbf{m}}\),a1d** \\ \end{tabular}  & \ \begin{tabular}{c} **Short-Term Water** \\ **Absorption,** \\ **W\({}^{\mathbf{w}}\),a2 sd** \\ \end{tabular}  & \begin{tabular}{c} **Long-Term Water** \\ **Absorption,** \\ **Conductivity,** \(\lambda\) \\ \end{tabular}  \\ \hline \multicolumn{2}{c}{kg/m\({}^{3}\)} & kPa & [kg/m\({}^{2}\)] & \%wt. & \%vol. & W/mK \\ \hline HERF & 246 \(\pm\) 23.8 & 176 \(\pm\) 21.2 & 4.79 \(\pm\) 0.431 & 123 \(\pm\) 11.1 & 59.3 \(\pm\) 5.34 & 0.054 \(\pm\) 0.0043 \\ \hline SD  
the composite with 100% WS, when mixed with HERF, also determines a lower thermal conductivity of about 0.043 W/m.K. When WS is mixed with SDLS and PS, this leads to a certain increase in the apparent density (by 11% to 13%) and a marginal increase in \(\lambda\) to 0.045 W/mK. The composites based on 100% HERF and 100% SDLS have significantly higher densities (123% and 67%, respectively), but the thermal conductivity does not increase proportionally and is 0.054 W/m.K and 0.049 W/mK, respectively. At the same time, the composites with 100% HERF and 100% SDLS have the best mechanical performance. The compressive resistance at 10% deformation is well above 100 kPa (up to 176 MPa), which would allow for use as thermal floor/roof insulation, as well as impact-born noise insulation. The porosity of those composites is relatively coarse because they have the highest capillary absorption, but the lowest short-term absorption after 24 h of immersion in water. Usually, the short-term water absorption is considered representative of finer porosity. As it has been observed during our preliminary studies [11], the cross-section of the SDLS-based mycelium composites showed the presence of more macro-pores, allowing a larger amount of hyphae inside the material. The structure of the HERF-based bio-composites was more compact and tougher, especially in the core of samples, leading to a higher apparent density of the mycelium HERF-based bio-composites. All results on the compressive resistance at 10% deformation fall within the limits of [PERSON] et al. [35], between 29 and 567 kPa, specified for different mycelium-based bio-composites. [PERSON] et al. [55] stated that the compressive strength of mycelium-based bio-composites was lower than that of most EPS categories; however, our results did not confirm this and actually demonstrated very close superior performance to EPS--at 100% HERF and 100% SDLS. When mixed substrate was used, the \(\sigma_{10}\) was still above 30 kPa, which is the most reported value for EPS wall thermal insulation. The highest capillary absorption is measured within 100% SDLS composite, followed by 100% HERF composite. It is determined not only by the open voids but also from the water suction by the used HERF and SDLS. Modifying porosity by adding 50% of WS to both HERF and SDLS substrates significantly reduces (by 40% and 75%, respectively) the capillary absorption of composites. The results obtained for these composites and the 100% WS composite are close to those reported by [PERSON] et al. [29] for mycelium-chopped hemp, flax- and straw-based bio-composites, having capillary absorption between 2 and  
Figure 3: Relationship between the thermal conductivity and apparent density of MBCs. 3.8 kg/m\({}^{2}\). Adding 50% of PS to the WS composite leads to more than a double increase in the capillary absorption of the composite. The short-term water absorption (after 1 day of immersion in water) is representative of the finer porosity of materials. The results on water absorption after one day of full immersion vary among the different composites between ca. 120 %wt and ca. 250 %wt, being lower for 100%HERF and SDLS-based composites and higher for WS-containing composites. It seems that the combination of different substrates is able to convert the course to a finer porosity, without reduction in the absorption capacity as a whole.