## 2 Methodology
### Sample Compositions and Material Properties
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Materials**} & \multirow{2}{*}{**Thickness**} & \multirow{2}{*}{**Density**} & \multicolumn{2}{c}{**Water-Vapour**} & \multirow{2}{*}{**Conductivity 1**} & \multirow{2}{*}{**Specific Heat**} & \multirow{2}{*}{**Porosity**} \\  & & & & & & & & \\ \cline{2-2} \cline{5-8}  & **(mm)** & **(kg/m\({}^{3}\))** & & & & & & \\ \cline{2-2} \cline{5-8}  & & & & & **20\%** & **50\%** & **80\%** & & \\ \hline
2.2.4 earth plaster & & & & & & & & \\ with straw & 0.008 & 1456 & 18 & 0.71 & 0.75 & 0.94 & 880 & 0.85 \\
3.1 earthen adhesive & 0.003 & 45 & 67 & 0.34 & 0.344 & 0.404 & 880 & 0.9 \\
3.2 wood & 0.020 & 232 & 6 & 0.047 & 0.048 & 0.051 & 1200 & 0.91 \\
3.3.2 flexible wood & & & & & & & & \\ fibreboard PaVraflex & & & & & & & & \\
3.6.3 gypsum fibreboard & 0.125 & 1200 & 15 & 0.22 & 0.23 & 0.24 & 800 & 0.53 \\
4.12 mineral wool ECOSE & 0.40 & 15 & 3 & 0.037 & 0.038 & 0.041 & 850 & 0.9 \\ \hline \hline \end{tabular}  
* Corresponding to three values of relative humidity: 20%, 50%, 80%.  
\end{table} 
Table 1: Material properties. Figure 1: Investigated wall assembly samples. with a gradually increasing relative humidity (50%, 65% and 90%), at a constant temperature of 23 \({}^{\circ}\)C. The moisture content in particular samples was not determined for humidity values higher than 90%, due to the fact that the MBV tests were carried out at a maximum moisture load of 80%. To measure the water content corresponding to the relative humidity, samples were first exposed to constant temperature and relative humidity conditions in a climate chamber with an accuracy of \(\pm\)0.5 \({}^{\circ}\)C and 3% RH. The eight samples were measured over a 24-h period until the change rate of the sample was smaller than the initial change rate at least three times in succession. Figure 2 shows the adsorption isotherms for all tested materials. The vapour diffusion resistance factors of the samples were determined according to the ISO 12572 standard [26]. The tests were carried out for each type of material on three samples with diameters 127-128 mm and thicknesses in the range of 40-80 mm. The samples were initially conditioned at 23 \({}^{\circ}\)C and 50% relative humidity, until they reached a constant mass. Then, the samples were placed in special metal dishes containing a desiccant (CaCl\({}_{2}\)). The sides of the insulation samples were sealed with wax. The prepared samples were exposed to a temperature of 20 \({}^{\circ}\)C with a relative humidity of 50%. Dishes were then weighed every 24 h until steady state was reached, when the difference between two consecutive weigh-ins became constant. The water-vapour resistance factor \(\mu\) was calculated according to Equation (2):  
\[\mu=\frac{\delta_{a}}{\delta}, \tag{2}\]  
where \(\mu\) is the water-vapour resistance factor, \(\delta\) is the water-vapour permeability (kg:m\({}^{-1}\) s\({}^{-1}\):Pa\({}^{-1}\)) and \(\delta_{a}\) is the water-vapour permeability of air with respect to the partial vapour pressure. The water-vapour permeability \(\delta\) is calculated using Equation (3):  
\[\delta=\frac{G\cdot d}{A\cdot\Delta p}, \tag{3}\]  
where \(G\) is the water-vapour flow rate (kg/s), \(d\) is the test specimen thickness (m), \(A\) is the exposed surface area (m\({}^{2}\)) and \(\Delta p\) is the pressure difference (Pa). The density was determined according to the EN 1602 standard [27]. The specimens were cut and preconditioned at 50% RH and 20 \({}^{\circ}\)C before being tested. The test consisted of weighing the samples, determining their volume and calculating the density as the quotient of mass and volume using Equation (4):  
\[\rho=\frac{W}{a\cdot b\cdot c}, \tag{4}\]  
where \(a\), \(b\), \(c\) (m) and \(W\) (kg) are the length, width, thickness and weight of the specimen, respectively. Figure 2: Water content according to relative humidity at 50%, 65% and 90%.