Cool façade optimization: A new parametric methodology for the urban heat island phenomenon (UHI)

In recent years, the urban climate has been progressively changing due to different causes that affect the environmental conditions. One consequence of this metamorphosis and the growing building density is known as the urban heat island (UHI) factor, which alters the quality of outdoor spaces due to the overheating of building surfaces. Microclimate features influence indoor activities and human heat stress. The research aims to provide an answer to the problem caused by excessive solar radiation on the urban fabric and the consequent UHI factor. The following study focuses on different façade characterizations based on various materials with relevant reflectance efficiencies that transform the exterior of buildings into 'cool façades'. The research considers the thermal performance of the building façade, the heat exchange between the building, and canyon surfaces as thermal masses in a new parametric methodology. Using thermodynamic tools connected by a parametric engine, the analysis demonstrates how cool façades reduce heat transfer to both the building and the environment. The study analyzes façade materials related to their shading capacity, high reflectivity, and emissivity in different urban canyon scenarios. Microclimates and outdoor comfort are monitored by measuring the canyon surface temperatures and the Universal Thermal Climate index (UTCI), which combines air temperature, humidity, mean radiant temperature, and wind speed. The indoor environment is observed using air temperatures. The study reveals how cool façades help to improve outdoor as well as indoor conditions.