## 2 Materials and Methods
### In-Field Measurements Results
#### 3.2.2 Test_1  
Test_1, which involved the activation of ventilation (4.5 ACH from 7 am to 8 am), was carried out between 7 and 13 October. Moreover, the day characterized by the highest solar radiation and by the highest internal/external temperatures was selected for detailed analysis (8 October). The following data were analyzed:  
* Surface temperatures (Ts)
* Heat flux (HF_m)
* PCM temperature (T_PCM)
* Mean radiant temperature (T\({}_{\rm{mr}}\))  
The monitored indoor surface temperature values of the roof are plotted in Figure 10a for the overall period. A reduction in the temperature peaks in Room B (PCM 23) and Room C (PCM 21), compared with the reference configuration (Room A), can easily be seen. Focusing the analysis on the reference day (Figure 10b), the maximum temperature reached in cell B (with Infinite R\({}^{\rm{TM}}\) 23-PCM Y) is \(\sim\)1.2 \({}^{\circ}\)C lower than the maximum value achieved in cell A (from 23.6 \({}^{\circ}\)C to 22.4 \({}^{\circ}\)C). A slightly more marked reduction of the temperature peak (about 1.5 \({}^{\circ}\)C) is achieved in Room C with Infinite R\({}^{\rm{TM}}\) 21 (from 23.6 \({}^{\circ}\)C to 22.1 \({}^{\circ}\)C). Figure 8: Boundary conditions: interior air temperature (T_int), external air temperature (T_ext), external relative humidity (RH_ext). Figure 9: Boundary conditions: horizontal solar irradiance (Sol_H), incident global solar irradiance (Sol_I). Another consideration can be made by looking at the temperature values collected in the night hours (from 21:00 to 23:00). The surface temperatures in Rooms B and C were slightly higher than those reached in Room A (without any PCM layer); this phenomenon maybe related to the release of the heat stored in the PCM during the day, which is released during the night-time and early morning hours. Moreover, the presence of the PCM in the layers leads to a shift of the temperature peaks: in reference Room (A), the maximum temperature is reached at 18:00, while a delay of about 45-60 min is observed in Rooms B and C.  
The heat flux analysis (Figure 11) shows a similar trend. The positive influence of the PCM can be observed during daytime, when a significant heat flux reduction (gains) occurs. A comparison of the data collected on the reference day (8 October) has revealed that:  
* a heat flux reduction of \(\sim\)40% (from 9.4 W/m\({}^{2}\) to 5.6 W/m\({}^{2}\)) can be achieved in the daily peak values, if Infinite RTM 23 (PCM Y) is applied (Room B). * a heat flux reduction of \(\sim\)48% (from 9.4 W/m\({}^{2}\) to 4.9 W/m\({}^{2}\)) can be achieved in the daily peak values, if Infinite RTM 21 (PCMX) is applied (Room C). The temperatures of the PCM layer, shown in Figure 12, are the values collected from the sensors located in the upper and lower sides of the PCM panel (Ts4 and Ts5). Figure 11: Monitored Heat fluxes (HF_m): (**a**) whole period; (**b**) the reference day (8/10). Figure 10: Internal surface temperature (Tsi) in the test rooms: (**a**) the whole period; (**b**) the reference day (8/10). A comparison with the enthalpy vs. temperature values was carried out to assess the exploitation of the PCM latent heat storage capacity. A lower temperature variation was noticed in the cell equipped with the Infinite RTM 21 layer (cell C), while the Infinite RTM 23 (cell B) showed a higher temperature variation. * Infinite RTM 23 (Room B) showed a temperature variation of between 16.8 \({}^{\circ}\)C (8:00) and 23 \({}^{\circ}\)C (16:30), with an amplitude of 6.2 \({}^{\circ}\)C.
* Infinite RTM 21 (Room C) showed a temperature variation of between 18.2 \({}^{\circ}\)C (8:00 am) and 21.5 \({}^{\circ}\)C (17:00 pm), with an amplitude of 3.2 \({}^{\circ}\)C.  
This behaviour is closely related to the different phase change temperatures of the two PCMs.