## 2 Materials and Testing Methods
### Thermal Characterization  
The apparatus named Small Hot-Box was used for thermal tests [23] (Figure 2); it was developed and calibrated by several preliminary measurements at the University of Perugia (Laboratory of Environmental Control, Department of Engineering), following some of the prescriptions of EN ISO 8990 [24]. A detailed description of the apparatus can be found in [9]. The thermal flux meter methodology is followed and the thermal conductivity is calculated considering the mean surface temperatures of the hot and cold sides (\(T_{sH}\) and \(T_{SC}\), respectively), the heat flux through the sample (\(q\)), and the total thickness of the specimen (\(s\)), as reported in (1):  
\[\lambda=\frac{q}{T_{sH}-T_{SC}}\cdot s_{sample}\left[\frac{\text{W}}{\text{mK}}\right] \tag{1}\]  
The panels not being self-bearing, it was necessary to use support layers (support layer 1 and support layer 2), especially for the more fragile materials: in these cases it was calculated the thermal contribution of only one layer (\(R_{sample}\)) from the total thermal resistance of the composed samples (\(R_{tot}\)), as reported in Equation (2):  
\[R_{tot}=R_{support\ 1}+R_{sample}+R_{support\ 2}=\frac{s_{support\ 1}}{\lambda_{ support\ 1}}+\frac{s_{sample}}{\lambda_{sample}}+\frac{s_{support\ 2}}{ \lambda_{support\ 2}}\qquad\left[\frac{\text{m}^{2}\text{K}}{\text{W}}\right] \tag{2}\]  
where:  
* \(R_{support\ 1}\), \(s_{support\ 1}\), and \(\lambda_{support\ 1}\) are, respectively, the thermal resistance (m\({}^{2}\)K/W), the thickness (m), and the thermal conductivity (W/mK) of the first support panel; \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Density (kg/m\({}^{3}\))**} & \multirow{2}{*}{**Granule Size** **(mm)**} & **Fire Reaction** & \multirow{2}{*}{**Calorific Value (kJ/kg)**} \\  & & **(mm)** & & **Class** \\ \hline COR & 130 & 8–10 & B2 & 17.000 \\ ELT & 600 & 1–2.5 & B2 & 42.000 \\ RH & 170 & 1–9 & A1 & 14.000 \\ CC & 78 & \textless{}0.5 & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Main characteristics of the loose materials [12; 16]. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Description of the Panels**} & \multirow{2}{*}{**Thickness (mm)**} & \multicolumn{4}{c}{**Weight Ratio (\%)**} \\ \cline{3-6}  & & & **COR** & **ELT** & **RH** & **CC** \\ \hline
1 & COR + RH & 52.7 & 70 & & 30 & \\
2 & COR + CC & 55.5 & 70 & & & 30 \\
3 & COR + ELT & 52.3 & 70 & 30 & & \\
4 & COR + ELT + RH & 51.0 & 40 & 30 & 30 & \\
5 & COR + CC + RH & 51.5 & 40 & 30 & 30 & \\
6 & COR + ELT +RH + CC & 52.3 & 40 & 20 & 20 & 20 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Weight ratio of the manufactured samples. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Description of the Panels**} & \multicolumn{4}{c}{**Quantities of the Material in the**} & \multicolumn{2}{c}{**Density of the**} \\  & & \multicolumn{4}{c}{**Mixtures (g)**} & \multicolumn{2}{c}{**Panels (kg/m\({}^{3}\))**} \\ \cline{2-7}  & **Glue** & **COR** & **ELT** & **RH** & **CC** \\ \hline
1 & COR + RH & 363 & 335 & & 143 & & 177.5 \\
2 & COR + CC & 579 & 437 & & & 187 & 240.8 \\
3 & COR + ELT & 371 & 428 & 184 & & & 208.8 \\
4 & COR + ELT +RH & 372 & 252 & 189 & 189 & & 218.4 \\
5 & COR + CC +RH & 741 & 257 & & 193 & 193 & 298.4 \\
6 & COR + ELT +RH + CC & 777 & 283 & 141 & 141 & 141 & 315.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Weights and densities of the manufactured samples. * \(R_{support}\) 2, \(S_{support}\) 2, and \(\lambda_{support}\) 2 are, respectively, the thermal resistance (m\({}^{2}\)K/W), the thickness (m), and the thermal conductivity (W/mK) of the second support panel;
* \(R_{sample}\), \(S_{sample}\), and \(\lambda_{sample}\) are, respectively, the thermal resistance (m\({}^{2}\)K/W), the thickness (m), and the thermal conductivity (W/mK) of the sample layer to be tested. Thermal properties of the support panels (\(\lambda_{support}\) 1 and \(\lambda_{support}\) 2) were measured in a laboratory following the same procedure.