The commitment to energy efficiency in buildings has become more relevant as a measure to mitigate the increase in temperature established by the Paris Climate Conference. This phenomenon has increased in historic buildings, which are not designed to maintain an acceptable level of thermal comfort for the occupants despite the recent increase in temperature, resulting in intensive energy use. This research evaluates the thermal performance of a passive cooling system in a historic religious building through a correlational method. The analysis included different occupancy levels and the climate model provided by the Intergovernmental Panel on Climate Change. The study considered meteorological data from the current scenario (2022) and two chronological progressions throughout the 21st century (2050, 2100). The meteorological database of future projections was collected by the Meteonorm software considering three climate change scenarios, specifically the Representative Concentration Pathways (RCP). The objective was to determine the effectiveness of the passive cooling system in mitigating climate change. The findings showed a reduction in radiative and conduction heat gains of 70 % in the current scenario and a decrease in temperature for the most unfavourable scenario (RCP 8.5 in 2100) between 1.4 °C and 1.9 °C. These results demonstrate the effectiveness of using efficient passive systems to mitigate climate change in temperate climates.