Adopting a multiscale approach is crucial for optimizing urban and building performance, prompting inquiries about the link between a technology’s local efficiency (building scale) and its broader impact (city-wide). To investigate this correlation and devise effective strategies for enhancing building and city energy performance, we experimentally examined a commercial nano-ceramic Thermal Barrier Coating (TBC) on a small-scale building and assessed numerically its influence on mitigating Urban Heat Islands (UHIs) at a city scale, translated in our case by the use of the thermal comfort index: the Universal Thermal Climate Index (UTCI). Our results reveal that the coating significantly curbs heat transfer locally, reducing surface temperatures by over 50 ∘C compared to traditional roofs and attenuating more than 70% of heat flux, potentially alleviating air conditioning demands and associated urban heat effects. However, implementing such coatings across a city does not notably advance overall efficiency and might trigger minor overheating on thermal perception. Hence, while nano-ceramic coatings indirectly aid UHI mitigation, they are not a standalone fix; instead, an integrated strategy involving efficient coatings, sustainable urban planning, and increased vegetation emerges as the optimal path toward creating enduringly sustainable, pleasant, and efficient urban environments to counter urban heat challenges effectively.