Façade Strategies for Climate Resilience: The Impact of Thermal Mass and Albedo on Urban Microclimates Across Different Climatic Zones

The intensification of thermal stress in cities due to urbanization and climate change underscores the urgent need to improve outdoor habitability. This study analyses the influence of three opaque façade technologies—traditional, lightweight and external thermal insulation composite systems—combined with two albedo levels (0.30 and 0.80), on summer outdoor conditions in Mendoza (Argentina), Madrid (Spain) and Campinas (Brazil). Using a calibrated microclimatic model with ENVI-met v5.6 software, a digital replica of a 10-storey urban canyon was simulated to generate 18 scenarios, assessing the effect of façade thermal mass and reflectivity on the urban microclimate. The results show that (i) scenarios that mainly affect air temperature (AT) are those that modify the thermal mass of the façade technologies. For example, traditional technology with a low albedo reduce maximum AT by up to 1.2 °C in Campinas, 0.89 °C in Mendoza, and 0.81 °C in Madrid compared to light technology with the same albedo level. (ii) Mean radiant temperature (MRT) increases significantly in scenarios involving lightweight façade by 4.53 °C in Madrid, 4.46 °C in Mendoza, and 3.39 °C in Campinas. Conversely, increasing façade albedo further amplifies MRT due to multiple reflections in urban canyons with increases of 6.50 °C in Campinas, 6.09 °C in Mendoza, and 5.33 °C in Madrid. The impact is more pronounced with traditional façades. (iii) Traditional façades and low-albedo ETIC systems experience the fewest hours of very high thermal stress (UTCI > 38 °C), whereas lightweight façades increase exposure to extreme heat. Overall, air temperature is primarily determined by façade thermal mass, mean radiant temperature by surface reflectivity, and thermal comfort by the combined effect of both. These findings confirm that high reflectivity can be counterproductive in dense urban canyons, emphasizing the importance of climate- and morphology-sensitive façade strategies for urban resilience.