# Energy Saving Potential of PCMs in Buildings under Future Climate Conditions
## 3 Materials and Methods  
### The Simulation Model  
The studied building is a Department of Energy (DOE) [45] medium office building model. It was selected from the U.S. Department of Energy Commercial Reference Building Models from the National Building Stock as the base case model for this energy simulation (Figure 1). The construction details of the lightweight building model are shown in Tables 1 and 2. The model modified according to a previous study [3], ANSI/ASHRAE standard 140-2011 [46], and EnergyPlus [47]. Three PCMs with different melting temperatures were evaluated, taking into account the heating and cooling set point temperatures of 20 \({}^{\circ}\)C and 26 \({}^{\circ}\)C, respectively: DuPonEnergainPCM (21.6 \({}^{\circ}\)C), RubITHERMPCM (25 \({}^{\circ}\)C)and BioPCM (29 \({}^{\circ}\)C). The physical properties of the PCMs are given in Table 3. A set of numerical simulations was conducted using the EnergyPlus software and assuming that each PCM was applied separately between the fiberglass quilt and plasterboard of the interior wall and roof (Figure 2). The interior environmental characteristics with and without PCM were analyzed to show the optimal method of PCM application. The PCM application in the building envelope was in a continuous layer of plastic encapsulation that looks like a mat. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **Material** & **Conductivity** & **Thickness** & **U** & **R** & **Density** & **Specific Heat** \\  & & **(W/m k)** & **(m)** & **(W/m\({}^{2}\) k)** & **(m\({}^{2}\) k/W)** & **(kg/m\({}^{3}\))** & **(f/kg k)** \\ \hline \multirow{6}{*}{Wall} & Int. surface coeff & - & - & 8.26 & 0.121 & - & - \\  & Plaster board & 0.160 & 0.012 & 13.33 & 0.075 & 950 & 840 \\  & Fiberglass quilt & 0.040 & 0.066 & 0.61 & 1.650 & 12 & 840 \\  & Wood stiding & 0.140 & 0.009 & 15.56 & 0.064 & 530 & 900 \\  & Ext. Surface coeff. & - & - & 29.41 & 0.034 & - & - \\  & Overall, air-to-air & - & - & 0.514 & 1.944 & - & - \\ \hline \multirow{6}{*}{Roof} & Int. surface coeff & - & - & 8.26 & 0.121 & - & - \\  & Plaster board & 0.160 & 0.01 & 16.00 & 0.063 & 950 & 840 \\ \cline{1-1}  & Fiberglass quilt & 0.040 & 0.1118 & 0.36 & 2.795 & 12 & 840 \\ \cline{1-1}  & Roof deck & 0.140 & 0.019 & 7.37 & 0.136 & 530 & 900 \\ \cline{1-1}  & Ext. Surface coeff. & - & - & 29.41 & 0.034 & - & - \\ \cline{1-1}  & Overall, air-to-air & - & - & 0.318 & 3.148 & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Wall and roof construction [3; 46; 47]. \begin{table}
\begin{tabular}{c c} \hline \hline
**Window Property** & **Value** \\ \hline Extinction Coefficient & 0.0196 mm \\ Number of panes & 2 \\ Pane thickness & 3.175 mm \\ Air-gap thickness & 13 mm \\ Index of refraction & 1.526 \\ Normal direct-beam transmittance through one pane & 0.86156 \\ Thermal conductivity of glass & 1.06 W/m k \\ Conductance of each glass pane & 333 W/m\({}^{2}\) k \\ Combined radiative and convective coefficient of air gap & 6.297 W/m\({}^{2}\) k \\ Exterior combined surface coefficient & 21.00 W/m\({}^{2}\) k \\ Interior combined surface coefficient & 8.29 W/m\({}^{2}\) k \\ U-value from interior air to ambient air & 3.0 W/m\({}^{2}\) k \\ Hemispherical infrared emittance of ordinary uncoated glass & 0.9 \\ Density of glass & 2500 kg/m\({}^{3}\) \\ Specific heat of glass & 750 j/kg k \\ Interior shade devices & None \\ Double-pane shading coefficient at normal incidence & 0.907 \\ Double-pane solar heat gain coefficient at normal incidence & 0.789 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Window construction in PCM-integrated buildings [3; 46; 47]. PCM: phase change material.