## 4 Methodology
### Integration in the EnergyPlus
#### 4.2.5 The Layers' Properties  
The Green Walls were represented as a simplified model, composed of two layers: foliage and substrate, spaced from the wall by an air gap. The foliage properties are different for each plant species, so two reference species have been analyzed: _Geranium Macrorrhizum_, associated with Light Systems because of its superficial roots, and _Bergenia Crassifolia_, linked to Heavy Systems because of the roots developing in depth. Thermal and physical properties were attributed to these layers comparing the results obtained by [PERSON] and [PERSON] [45] and [PERSON] et al. [46] for some plant species' leaves. Table 3 shows the properties obtained for the two reference species.  
The study of the thermophysical properties of the soil, whose contribution is substantial due to its thermal mass, was carried out after a literature review [59; 60; 61; 62; 63; 64; 65]. Three types of soil have been analyzed in this study: sandy loam, loam and clay loam, suitable for cultivation, and for each one, a defined density was fixed, thermal conductivity and specific heat. For the two species selected, the composition of soil was chosen according to the plant considered, to ensure its proper growth. The properties of soil are related to its water content, that must be included in a specific range to allow the plants to fulfill their vital functions: between 5% and 10% for sandy soils and between 40% and 50% for clay soils, as stated by [PERSON] [65]. These values were used to find a linear correlation between sandy and clay soils, to identify the correct saturation percentage of the simulated soils as shown in Figure 2.  
Other properties related to each soil, were obtained analyzing the studies carried out by [PERSON] [61], [PERSON] [59] and [PERSON] [50]; the results are shown in Table 4.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Properties**} & \multirow{2}{*}{**Units**} & \multicolumn{2}{c}{_Bergenia Crassifolia_} & \multicolumn{2}{c}{_Geranium Macrorrhizum_} \\ \cline{3-8}  & & \multicolumn{2}{c}{_Sandy loam_} & \multicolumn{2}{c}{_Loam_} & \multicolumn{2}{c}{_Clay loam_} \\ \hline \multirow{2}{*}{\% Saturation} & \multirow{2}{*}{-} & min & max & min & max & min & max \\  & & 10 & 20 & 20 & 30 & 30 & 40 \\ \hline Density & kg & 1700 & 1800 & 1800 & 1900 & 1900 & 2000 \\ \hline Thermal conductivity & \(\frac{\mathrm{W}}{\mathrm{m}\cdot\mathrm{K}}\) & 1.26 & 2.03 & 1.02 & 1.22 & 1.34 & 1.45 \\ \hline Specific heat & \(\frac{\mathrm{I}}{\mathrm{kg}\cdot\mathrm{K}}\) & 1125 & 1328 & 1080 & 1209 & 1324 & 1465 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Properties of cultivated soil (sandy loam, loam, clay loam) related to saturation percentage of pores.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Properties**} & \multirow{2}{*}{**Units**} & \multicolumn{2}{c}{_Bergenia_} & \multicolumn{2}{c}{_Geranium_} \\  & & _Crassifolia_ & _Macrorrhizum_ \\ \hline Single leaf thickness & m\(\cdot 10^{-3}\) & 0.25 & 0.21 \\ \hline Canopy layer thickness & m\(\cdot 10^{-3}\) & 5 & 5 \\ \hline Thermal conductivity & W\(\cdot\)m\({}^{-1}\cdot\mathrm{K}^{-1}\) & 0.34 & 0.35 \\ \hline Density & kg\(\cdot\)m\({}^{-3}\) & 656 & 627 \\ \hline Specific heat & J\(\cdot\)kg\({}^{-1}\cdot\mathrm{K}^{-1}\) & 2252 & 2232 \\ \hline Thermal effusivity & W\(\cdot\)s\({}^{\frac{1}{2}}\cdot\)m\({}^{-2}\cdot\mathrm{K}^{-1}\) & 714 & 702 \\ \hline Thermal diffusivity & m\({}^{2}\cdot\)s\({}^{-1}\cdot 10^{-6}\) & 0.23 & 0.25 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Variation range for the variable parameters that influence solar absorptance coefficient and related references.  
Figure 2: The optimal range of saturation percentage for each type of soil, to guarantee plant survival, is represented by the rectangular boxes; instead, the values indicated as a line generate stress in plants.