## 4 Conclusions
Moreover, the effect of natural ventilation on the thermal performance of the component has been analyzed. The first monitoring period was characterized by higher external temperatures and activation of the ventilation system, which led to an improvement of the PCM discharging process. A better exploitation of the PCM storage capacity was seen during this first period. In the second monitoring period, due to the lower outdoor temperatures, a less evident improvement of the indoor conditions was observed in the components with PCM. The comparison of the heat fluxes and temperatures between the reference cell (without PCM) and those equipped with Infinite RTM 21 and Infinite RTM 23 has demonstrated that the adoption of these materials allows both the temperature and the heat flux peaks to be reduced. In particular:  
* PCM Infinite RTM 21 (room C) always shows a higher potential for reducing the peak heat gains (up to 47-48% for both monitoring periods) and a reduction in the internal surface temperature of the roof of up to 1.5 \({}^{\circ}\)C.
* PCM Infinite RTM 23 (room B) shows a lower peak heat gain reduction (about 20-40%, depending on the monitoring period) and reductions in the internal surface temperature of the roof of \(\sim\)1.2 \({}^{\circ}\)C (test period #1) and \(\sim\)0.6 \({}^{\circ}\)C (test period #2). These outcomes should clearly be related to the range of the outdoor/indoor temperatures, since the results could change significantly for different climatic conditions or in a different season. It should be noted that the latent heat capacity of the PCMs was never fully exploited in any of the monitoring periods. Only for PCM Infinite RTM 21 (Room C) was a partial exploitation seen. Therefore, although some benefits can be highlighted, it is worth mentioning that a better performance can be obtained if the right PCM melting temperature is selected. This leads to the consideration that the melting temperature of PCMs, as well as their quantity and position need to be carefully designed to achieve a better performance and to gain greater benefits, in terms of both the indoor thermal comfort conditions and energy saving. In relation to this latter remark, a graphical tool that is useful to help choose the most promising PCM is proposed in Figures 12 and 16. In these plots, the trends of the temperature vs. the enthalpy of the PCM, T(h) (for heating and cooling) are \"overlapped\" onto the trend of the temperature of the component vs. time, T(time). This allows clear information to be obtained, at a glance, concerning to what extent the potentialities of the phase change process are exploited. In order to optimize the behavior of the component, the peaks of function T(h) should be within the range of fluctuations of the temperature over time, T(time), as much as possible, in such a way that, at each oscillation, most of the heat of fusion of the PCM is exploited. The conclusions that have been discussed above are represented in Figure 12a,b and Figure 16a,b. The \"overlap\" of the two functions, that is, of T(h) and T(time), is significantly higher in Figures 12b and 16b (Infinite \(\mathrm{R}^{\mathrm{TM}}\) 21, Room C) than in Figures 12a and 16a (Infinite \(\mathrm{R}^{\mathrm{TM}}\) 23, Room C). Conceptualization, S.F., G.A. and E.F.; methodology, S.F., E.S. and G.A. ; formal analysis, S.F., E.S., G.A. and E.F.; investigation, S.F., E.S. and G.A. ; data curation, S.F., E.S., G.A. and E.F.; writing--original draft preparation, S.F., G.A. and E.F.; writing--review and editing, S.F., M.P. and E.F.; visualization, G.A. and E.F.; supervision, S.F. and M.P. All authors have read and agreed to the published version of the manuscript. This research was partially funded by the E4E S.r.l. company in the framework of a consultancy contract with the Politecnico di Torino--Department of Energy, under the scientific responsibility of [PERSON] (2021). The authors wish to thank [PERSON] and [PERSON] of E4E S.r.l. for the support provided during the research activities. The authors declare no conflict of interest.