## 2 Methodology
### WUFI Software
Therefore, for one-dimensional heat and moisture transport, the following two-equation system is obtained [6]:  
\[\frac{\partial H}{\partial\theta}\cdot\frac{\partial\theta}{\partial t}= \frac{\partial}{\partial x}\bigg{(}\lambda\cdot\frac{\partial\theta}{ \partial x}\bigg{)}+h_{\text{p}}\cdot\frac{\partial}{\partial x}\bigg{(} \delta_{p}\cdot\frac{\partial}{\partial x}(\varphi\cdot p_{\text{p},sat}) \bigg{)} \tag{1}\]  
\[\frac{\partial w}{\partial\varphi}\cdot\frac{\partial\varphi}{\partial t}= \frac{\partial}{\partial x}\bigg{(}D_{\varphi}\cdot\frac{\partial\varphi}{ \partial x}+\delta_{p}\cdot\frac{\partial}{\partial x}(\varphi\cdot p_{\text{ v},sat})\bigg{)} \tag{2}\]  
where \(\partial H/\partial\theta\) is the heat storage capacity of the moist building material (J/(m\({}^{3}\)K)), \(H\) is the total enthalpy (J/m\({}^{3}\)), \(\theta\) is the temperature (\({}^{\circ}\)C), \(t\) is the time (s), \(\lambda\) is the thermal conductivity of the moist building material (W/(m\(\cdot\)K)), \(h_{\text{p}}\) is the evaporation heat of water (J/kg), \(\delta_{p}\) is the water vapour permeability of a building material (kg/(m\(\cdot\)s\(\cdot\)Pa)), \(\varphi\) is the relative humidity (-), \(p_{\text{v},sat}\) is the vapour saturation pressure (Pa), \(\bar{\omega}w/\partial\varphi\) is the moisture storage capacity of the building material (kg/m\({}^{3}\)), and \(D\varphi\) is the liquid conduction coefficient of the moist building material (kg/(m\(\cdot\)s)). WUFI is an extremally used software to assess the hygothermal performance of assemblies in countries, for example, Norway. This user-friendly software has been validated by experimental campaigns (e.g., [32]), by comparison with other software (e.g., [33]), and against EN 15026 [34]. Finally, the software has been subjected to several updates across the years [35], which allows it to stay up-to-date in this ever-evolving scientific field. The material properties are divided into two categories [9]. Basic properties, essential for the program, and advance properties, which can be left out. However, their omission has significant consequences for the results. The advance properties are the moisture storage function, the liquid transport coefficient for suction and for redistribution, the moisture-dependent thermal conductivity, and the moisture-dependent vapour diffusion resistance factor. The latter, in the simulated materials, is accounted for in the liquid coefficients [9]. The liquid transport coefficient of a material changes in accordance with if it is constantly supplied with water (e.g., rain event) or not. During a rain event, since a great amount of water is supplied to the material and due to their lower flow resistance, the liquid transport is governed by the larger pores [36]. On the other hand, in the absence of a water supply, the liquid transport is governed by the smaller pores due to their higher capillary pressure [36]. WUFI uses the liquid transport coefficients for suction (D\({}_{\text{ws}}\)) when water is constantly supplied to the material, and otherwise, it uses the liquid transport coefficients for redistribution (D\({}_{\text{ww}}\)); both these coefficients are highly moisture dependent. The liquid transport coefficients for each of the simulated materials are featured in Figure 3 and their water absorption coefficient in Table 1.  
Surface transport coefficients describe heat and moisture exchanges between a wall surface and the ambience [37]. They differ in exterior and interior ambiences. For an exterior surface, the program considers the surface heat resistance, short-wave radiation absorptivity, long-wave radiation emissivity, and rain water absorption factor. For an interior surface, the program only considers the heat resistance. WUFI can consider the long-wave radiation exchanges between an exterior surface and its surroundings in three different ways [9; 38; 39]: the heat transfer coefficient, the simplified method, and the explicit radiation balance method.