## 2 Materials and Methods
### In-Field Test Room Analysis
#### 2.2.1 Experimental Set-Up  
The monitoring campaign was carried out in three identical test cells (Figure 2), named TRIS (Testing Roofing Innovative Systems), located in the north of Italy (San Francesco al Campo, Turin). The cells were specifically built to assess and compare the thermal performance of different roof layouts by monitoring various parameters (temperature and heat fluxes). The monitoring campaign was carried out in October 2020 for about two non-consecutive weeks. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**PCM Type**} & \multirow{2}{*}{**Test**} & \multirow{2}{*}{**Number of Set**} & \multicolumn{2}{c}{**Initial**} & \multicolumn{2}{c}{**Final**} & \multicolumn{2}{c}{**T\({}_{\text{average}}\) [\({}^{\circ}\)C]**} \\ \cline{3-10}  & & & **Points** & **T\({}_{\text{1}}\)** [\({}^{\circ}\)C] & **T\({}_{\text{2}}\)** [\({}^{\circ}\)C] & **T\({}_{\text{1}}\)** [\({}^{\circ}\)C] & **T\({}_{\text{2}}\)** [\({}^{\circ}\)C] & **Initial** & **Final** \\ \hline \multirow{2}{*}{X} & Melting & 17 & 15.5 & 16.5 & 31.5 & 32.5 & 16 & 32 \\  & Solidification & 17 & 32.5 & 31.5 & 16.5 & 15.5 & 32 & 16 \\ \hline \multirow{2}{*}{Y} & Melting & 17 & 15.5 & 16.5 & 31.5 & 32.5 & 16 & 32 \\  & Solidification & 17 & 32.5 & 31.5 & 16.5 & 15.5 & 32 & 16 \\ \hline \multirow{2}{*}{C} & Melting & 17 & 15.5 & 16.5 & 31.5 & 32.5 & 16 & 32 \\  & Solidification & 17 & 32.5 & 31.5 & 16.5 & 15.5 & 32 & 16 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The set-point temperatures (T) used to assess the enthalpy function for samples X, Y, and Z. Three different layouts of the rooftop, characterized by the same dimensions, were installed in each test cell, and were equipped with a set of sensors to fully assess the thermal behaviour of each roof configuration. The three monitored configurations were:  
* Cell A: Reference without any PCM
* Cell B: PCM Infinite RTM 23 (PCM Type \"Y\")
* Cell C: PCM Infinite RTM 21 (PCM Type \"X\")  
Details of the different layers of each roof in the test cells are given in Table 4.  
The outdoor boundary conditions were measured by a weather station and by two pyranometer sensors (Hukseflux LP02) for the incident (sloped) and horizontal global solar radiation (Figure 3a). Type-T thermocouples were installed in the test rooms to monitor the internal air temperature and the temperature of each interior surface. In addition, several thermocouples were installed in the interface between the roof layers (Figure 4b). Moreover, heat flux sensors (Hukseflux HFP01) were placed on the internal side of the panels to assess and compare the heat gains and losses for the three monitored configurations (Figure 3b). The sensors were connected to a data-logging system (Datataker DT85 with a CEM channel expansion module) which collected data at a timestep of 15 min. The collected data were analyzed, and a comparison between rooms A, B and C was performed to assess the impact of the PCM on the temperatures and heat fluxes. The names of the sensors are shown in Figure 4a. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Material** & **Cell A** & **Cell B** & **Cell C** \\ \hline
1 & Clay tiles & 30 mm & 30 mm & 30 mm \\
2 & Slightly ventilated air cavity & 70 mm & 70 mm & 70 mm \\
3 & Extruded Polystyrene (XPS) & 50 mm & 50 mm & 50 mm \\
4 & PCM & no PCM & \(\sim\)7 mm (Infinite RTM 23, & \(\sim\)7 mm (Infinite RTM 21, & \\  & & & PCM Type “Y”) & PCM Type “X”) \\
5 & Gypsum board & 12.5 mm & 12.5 mm & 12.5 mm \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Layout of the monitored TRIS rooftop. Figure 2: (a) The TRIS apparatus; (b) View of the internal space of a cell; (c) Installation of the Infinite RTM panels.