On microsphere based advanced coatings for mitigating urban overheating

The urban heat island phenomenon arises from the collective impact of heat-absorbing materials in urban areas, heightened industrial and human activities, ongoing urban development that reduces green spaces, and inadequate air circulation. This phenomenon leads to a gradual rise in microclimate temperatures within heavily urbanized regions, resulting in significant temperature disparities when compared to rural areas. Reducing heat waves and enhancing urban comfort can be achieved by employing highly reflective and emissive materials in buildings, effectively minimizing heat generation within cities. To this aim, this study develops innovative coatings integrating different types of microspheres. This approach seeks to identify the ideal combination to achieve maximum performance for building application components. To achieve this goal, an evaluation was conducted on innovative coatings incorporating microspheres composed of glass, ceramic and chromium stainless steel. Specifically, these microspheres were examined in a size range from approximately 10 to 800 μm and were applied in varying concentrations on the base layer. To ensure a comprehensive evaluation, analyzes including spectrophotometry, FTIR spectroscopy and profilometry were conducted. This approach allowed the solar reflectance, thermal emittance, and distribution and final roughness of the proposed coatings to be evaluated in detail. The main results identified how the base layer interacted with the supplementary materials. The concentration of the applied microspheres proved to be fundamental in the results of the profilometric parameters, affecting in particular the surface roughness of the samples. At the same time, increased roughness led to a reduction in solar reflectance. Furthermore, the size of the microspheres not only influenced these parameters but also significantly influenced the thermal emissivity results. Therefore, the use of these coatings represents an effective strategy to address the urban heat island effect, adapted to local environmental conditions. The application of these coatings for specific spectral windows represents a promising approach to improve the performance of external building elements.