## 1 Introduction  
The building and civil construction sectors were responsible for around 30% of final energy use and 27% of CO2 emissions worldwide in 2021 [1]. In the Brazilian context, for the same year, buildings comprised around 51% of the country's final electricity consumption [2]. Global consumption with air-conditioning and ventilation in 2021 corresponded to roughly 16% of the final use of electricity in buildings, equivalent to 10% of the total electricity use in the world in that same year [3]. Given the worsening of climate change and extreme temperature events, the demand for air-conditioning systems only tends to grow, and, in the next three decades, the use of air-conditioning systems will be one of the main drivers of global electricity demand [4]. For the building sector to comply with and contribute to the net zero scenarios planned for 2030 onward, significant efforts must be implemented throughout the production and operational chain. The existential \"paradox\" of air-conditioning systems, which simultaneously guarantee comfortable climates and indoor conditions but reject the heat into an increasingly hotter atmosphere, denotes the imperative of applying energy efficiency measures and technological harmony in buildings and their systems. In response to this, the search for passive and active alternatives that ensure the thermal resilience of the built environment and thermal comfort over the long term, taking into account future climate changes, must be applied since the building's conception. Accordingly, the envelope contributes to around 60% of the energy cost during the life cycle of a building [5]. The appropriate project incorporating high-performance envelope technology is the most effective strategy to mitigate the thermal needs of buildings and ensure the comfort of occupants [6]. Envelope incorporation of thermal energy storage through latent heat using Phase Change Materials (PCM) is considered an advanced and promising technology [7]. With this stated, this paper aims to evaluate the thermal and energetic performance of a building with different proposed envelopes, using phase change materials, considering future climate change scenarios of distinct climates in Brazil. The building object of study represents the typology of a medium office building and has an energy model characterized by a single geometry. However, it has construction and heating, ventilation, and air-conditioning (HVAC) systems in line with the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) standards. The models suitable for the different climates in Brazil are simulated using the EnergyPlus software, version 9.2 [8], in the cities of Cunitiba and Rio de Janeiro, representing, respectively, bioclimatic zones 1 and 8, according to the Brazilian Association of Technical Standards (ABNT). By default, the buildings rely on purely resistive thermal insulation to adapt the thermal parameters of the external walls and roof established by ASHRAE. The work aims to compare the performances of the reference building without any insulating material with the designed resistive thermal insulator and the same building in which a PCM geometrically replaces the insulator. The same PCM is applied in both climatic regions, and its operating temperature matches the setpoints of the existing air-conditioning system. Projections for climate change are incorporated into the simulations through the climate files, using the statistical morphing process and data from the A2 (medium-high) emissions scenario, defined and made available by the Intergovernmental Panel on Climate Change (IPCC). The process is carried out using the CCWorldWeatherGen tool, version 1.9 [9], from the University of Southampton [10]. Two periods of climate change are constructed for the reference years of 2050 and 2080, taking the TMYx-type climate file as the basis for changes.