## 2 Materials and Methods
### In-Field Test Room Analysis
#### 2.2.2 Monitoring Period and Performed Tests  
The monitoring campaign was carried out in October 2020 over two non-consecutive weeks. Two different tests were carried out with different ventilation strategies under free-running conditions. Details of the different ventilation strategies are shown in Table 6:  
* Test_1 (7-13 October): mechanical ventilation system switched ON from 7:00 am to 8:00 am. The air change rate (ACH) was \(\sim\)4.5 [L/h]. This condition was intended to simulate opening the windows during the morning to cool down the buildings through airing. * Test_2 (16-21 October): ventilation OFF and just air infiltration with the outdoors (an airtight taping system was applied to minimize infiltration from the outdoor environment, therefore minimizing the ACH). \begin{table}
\begin{tabular}{c c c c} \hline  & & **Test\_1** & **Test\_2** \\ \hline Period & - & 7–13 October & 16–21 October \\ \hline Internal loads & [internal LED lamp 19 W] & ON (6:00–20:00) & ON (6:00–20:00) \\ \hline \multirow{2}{*}{Ventilation} & Schedule & ON (7:00–8:00) & OFF (00:00–24:00) \\ \cline{2-4}  & \multicolumn{1}{c}{Ventilation rate (ACH)} & \(\sim\)4.5 [L/h] & - \\ \hline \end{tabular}
\end{table} 
Table 6: Summary of the two test conditions. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**PCM Type**} & **Test** & **Heat Flux Direction** & **T\({}_{\text{up}}\)** & **T\({}_{\text{low}}\)** & **T\({}_{\text{avg}}\)** & \(\lambda_{\text{eq}}\)** & **\(\lambda_{\text{eq}\_avg}\)** \\  & & **Direction** & [\({}^{\circ}\)C] & [\({}^{\circ}\)C] & [\({}^{\circ}\)C] & [W/mK] & [W/mK] \\ \hline \multirow{4}{*}{X} & Test 1 (solid) & upward & 10 & 20 & 15 & 0.176 \(\pm\) 0.004 & \multirow{2}{*}{0.176 \(\pm\) 0.004} \\  & & downward & 20 & 10 & 15 & 0.175 \(\pm\) 0.004 & \\ \cline{2-6}  & Test 2 (liquid) & upward & 26 & 36 & 31 & 0.186 \(\pm\) 0.005 & \multirow{2}{*}{0.186 \(\pm\) 0.005} \\  & & downward & 36 & 26 & 31 & 0.186 \(\pm\) 0.005 & \\ \hline \multirow{4}{*}{Y} & Test 1 (solid) & upward & 14 & 24 & 19 & 0.221 \(\pm\) 0.005 & \multirow{2}{*}{0.220 \(\pm\) 0.005} \\  & & downward & 24 & 14 & 19 & 0.219 \(\pm\) 0.005 & \\ \cline{2-6}  & Test 2 (liquid) & upward & 30 & 40 & 35 & 0.209 \(\pm\) 0.005 & \\ \cline{2-6}  & & downward & 40 & 30 & 35 & 0.208 \(\pm\) 0.005 & \\ \hline \multirow{4}{*}{Z} & Test 1 (solid) & upward & 14 & 24 & 19 & 0.153 \(\pm\) 0.008 & \multirow{2}{*}{0.150 \(\pm\) 0.008} \\  & & downward & 24 & 14 & 19 & 0.146 \(\pm\) 0.008 & \\ \cline{1-1} \cline{2-6}  & Test 2 (liquid) & upward & 30 & 40 & 35 & 0.191 \(\pm\) 0.012 & \\ \cline{1-1} \cline{2-6}  & & downward & 40 & 30 & 35 & 0.195 \(\pm\) 0.012 & \\ \hline \end{tabular}
\end{table} 
Table 7: Equivalent thermal conductivity test results. \begin{table}
\begin{tabular}{c c} \hline
**Surface** & **View Factors [-]** \\ \hline Wall-Left & 0.311 \\ Wall-Right & 0.311 \\ Wall-Front & 0.087 \\ Door & 0.108 \\ Floor & 0.087 \\ Ceiling & 0.096 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The calculated view factors, \(F_{ij}\). Since a negligible difference was detected between the data measured during the tests with upward heat flux and those with downward heat flux, an average between the two data sets is provided (\(\lambda_{\text{eq,avg}}\)). As it is possible to observe, the equivalent thermal conductivity of the three PCM samples ranges between 0.150 W/mK (PCM Z solid) and 0.220 W/mK (PCM Y solid). The results show that the difference between the values measured in the liquid and solid-states is relatively small (about 5%) for PCM X and PCM Y. Instead, it is worth mentioning that PCM Z, with a nominal melting temperature of 25 \({}^{\circ}\)C, shows a greater difference between the solid and the liquid states test (the liquid thermal conductivity is about 29% higher than the solid one). Compared with literature data, all the measured thermal conductivity results were significantly lower than expected.