Vertical urban development in downtown Santiago has led to dense building areas that are prone to overheating, as their envelopes include multiple surfaces that absorb solar radiation. This increases energy consumption and exacerbates the urban heat island (UHI) effect. Often overlooked and underutilized, interior courtyards offer valuable opportunities for implementing passive design strategies by integrating green systems on their façades, thus enhancing thermal regulation. In this study, we developed a catalogue of interior courtyards within a defined sector near the city’s historic center, classified according to their height, width, and the ratio between these dimensions. The selected courtyards were either rectangular or square, located within medium-rise buildings ranging from five to twelve stories. We employed the ENVI-MET software (v.5.6.1) to assess the impact of direct and indirect green façades on thermal performance and comfort levels. Our results show that, in the rectangular courtyard with an indirect green façade, air temperature dropped by 9.2 ℃ compared to outdoor conditions and by 6.5 ℃ relative to the original courtyard scenario. On the outer wall surfaces, temperature reductions reached 11.4 ℃, while inner surfaces showed decreases of 5.8 ℃. For the square courtyard configuration, temperature reductions were even more significant: 10.9 ℃ and 7.2 ℃ in air temperature, and 11.2 ℃ and 6 ℃ on wall surfaces, respectively. We conclude that the square courtyard configuration is the most effective in enhancing cooling, and this study highlights the potential of passive design strategies—such as green façades—in improving thermal comfort and reducing energy demand in Mediterranean climates.