## 4 Conclusions  
This paper covers the need for real-scale experimental studies to determine the impact of PCM glazing on energy performance and the occupants' comfort of actual office buildings. This article presents an extensive empirical analysis of the effects of PCM glazing on energy consumption and thermal and visual comfort in an office room located in Santiago, Chile, a semiarid climate. PCM glazing corresponds to clear double glazing filled with paraffin RT25. Two rooms were monitored over a year: the PCM room equipped with the PCM window and the AIR room with clear double glazing. The main findings of this paper are:  
* Regarding energy consumption, the best PCM window performance was in summer when cooling needs and the peak loads of the PCM room were significantly decreased compared to the AIR room. Furthermore, in mid-seasons, PCM helped to reduce the cooling needs slightly for sunny and partly cloudy days and lower the heating needs at the end of working hours. In contrast, no relevant impact of the PCM window on the office energy performance was found in winter due to the lack of enough solar radiation and low outdoor air temperature to activate the phase change, even on sunny days. It is expected that a PCM with a higher melting temperature would show better results in summer, further decreasing the cooling energy use and the peak load. Nevertheless, the benefits of the PCM window would be lost during the mid-seasons. * PCM glazing considerably improves thermal comfort in terms of PMV and PMV\({}^{\star}\) compared to the reference window. This improvement is because the PCM phase change occurs mainly during the first hours of the day when direct solar radiation is incident on the east-oriented facade. Therefore, the mean radiant temperature remains close to the melting temperature of 25 \({}^{\circ}\)C. Moreover, PCM in the solid-state prevented most solar radiation transmission into the indoor environment, maintaining a PMV\({}^{\star}\) close to zero. * PCM glazing helps to control luminance distribution and prevent glare during sunny and partly cloudy days of winter and mid-season cold, keeping the DGP values below 0.25. Otherwise, PCM glazing did not present improvements in visual comfort regarding the reference window during summer and mid-season warm because both windows had similar luminance distributions during the whole day. Thus, DGP values are similar in both offices. Under direct solar radiation in the field of view and with the PCM in the solid-state, high luminance values were observed on the window. Interreflections of the direct radiation in the PCM layer might produce a significant fraction of the direct radiation that would be transmitted to the indoor environment. Then, there is glare risk in the PCM room as well as in the AIR room. Figure 14: (**a**) Relation between daily energy savings and daily maximum outdoor temperature. (**b**) Relation between daily energy savings and daily total global horizontal irradiance. In summary, the main benefits of the PCM inside the cavity of a double-glazed facade are (1) improving the occupants' thermal comfort, (2) reducing the cooling energy consumption and the peak loads during summer, and (3) preventing glare in the winter season. These benefits are caused by the PCM window's higher thermal inertia and the PCM's solid-state during the morning hours. This study fills the gap of experimentally evaluating the effects of PCM windows on offices' energy consumption and occupants' comfort. Furthermore, the results presented in this paper allow a better understanding of the PCM window performance toward the development and implementation of this technology. The developed experimental methodology is robust and reliable; thus, it can be replicated in other buildings in different climates to generate insightful information linked to the building function and climates. Further work must consider the study of other types of PCM, facade orientations, different climates, the comparison against smart/adapative facades, and cost-effectiveness analysis.