Optimized retro-reflective tiles for building application

Highly reflective materials have been proposed as a strategy for urban heat island (UHI) phenomenon mitigation. The effectiveness of a cool treated surface exposed to sunlight has been widely studied in terms of reduction of the surface temperature, reduction of cooling energy demand in conditioned buildings, improved indoor comfort and reduced UHI intensity. New researches proposed directional reflective materials, and in particular retro-reflective (RR) materials as innovative cool materials. Because of their directionality, their cool performance is mostly effective in urban patterns with buildings of different heights and with deep canyons, where typical cool diffusive materials are less effective. Previous studies investigated the performance of commercially available RR sheets typically used for street signs. The present study is aimed at investigating the performance of optimized RR materials for building application. An exterior ceramic tile has been provided with glass beads: glass spheres (Glass) and clear solid barium titanate spheres (Barium). The samples have been prepared spreading out the microspheres on a wet transparent UV resistant paint, with randomly placed spheres. One benefit of using randomly placed spheres is that the reflectivity has a higher cone of viewing than that of commercially available RR tapes. The angular reflectance of the retro-reflective samples is examined. A colorimetric analysis has been carried out to consider their applicability. The experimental characterization showed that the optimized RR materials applied on building envelope can reduce the energy trapped within the urban canopy and thus reduce the UHI effect. Further investigations are foreseen to optimize the process to produce industrial retro-reflective materials for building application.