## 1 Introduction
To understand the climatic consequences and the responses of the cited envelopes, energy consumption with the HVAC systems and the net heat balance across the surfaces of the north and south facades and roof are studied on a monthly scale. Mean radiant temperatures, operative temperatures, and heat fluxes through the internal faces of envelope surfaces in characteristic thermal zones are evaluated on an hourly scale, during a typical week, to assess the reasons for the different consumption and net heat balance profiles. Emphasizing the PCM application, the behavior of the material's physical state applied to each surface is studied to understand the reaction of the selected material to future climates and its impact on other metrics. According to a study from 2022 [11], for the climate projected for the year 2060 in several European cities, an increase between 99 and 380% in the cooling thermal load is estimated, while the opposite behavior can be observed for the heating load, which has an estimated reduction between 38 and 57%, depending on the typology and location. The results demonstrate that zero-energy buildings with lower insulation levels are less sensitive to climate change. Accordingly, buildings in hot climates in southern Italy, within the legal limits for the envelope, will suffer from overheating in the future (2080 projection), leading to disproportionate energy consumption with air conditioning [12]. Regulatory limits for envelopes have shown trends toward increasing thermal insulation, characterized by low thermal transmittance. Among the solutions that can be implemented in the envelope, it is possible to mention the increase in the thermal mass of the surfaces--improving the energy storage and thermal lag--and the increase in the thermal resistance of the layers of these surfaces--reducing heat transfer by conduction [13]. Although common construction materials can store thermal energy spontaneously as sensible heat, the use of latent heat is considerably more interesting from the point of view of the energy density of the process [14]. Bulk thermal insulators are capable of significantly reducing heat flow; on the other hand, they have little influence on energy storage [15]. In this context, the utilization of phase change materials to store thermal energy through latent heat presents a compelling option for mitigating thermal loads associated with heating and cooling, providing an innovative alternative to traditional envelope construction. Phase change materials have a dynamic behavior, as they can change their physical state at a specific and almost constant operating temperature during the process. Therefore, the passive or active use of PCM, linked to other strategies, can favor their application scenarios. A study from 2021 [16] evaluated the impact of applying PCM on the thermal comfort of a public school with a standardized project in Brazil's bioclimate regions 1 and 8 [17], also with Curitiba and Rio de Janeiro as representative cities. The buildings did not have mechanical HVAC systems and used natural ventilation to maintain thermal comfort, assessed based on 2017's ASHRAE Standard 55: Thermal Environmental Conditions for Human Occupancy [18]. The authors report that the PCM with a melting temperature of 21 \({}^{\circ}\)C obtained significant results in improving thermal comfort in both cities when applied to the external walls with a thickness of 5 cm. For the city of Rio de Janeiro, the PCM with a melting temperature of 27 \({}^{\circ}\)C also demonstrated a reduction in thermal discomfort hours when applied to the roof, also 5 cm thick.