Optimized retro-reflective tiles for exterior building element

Retro-reflective (RR) materials are innovative cool materials with the ability of reflecting most of the striking energy backwards and reducing the thermal energy kept inside the urban canopy. The present work is aimed at introducing new optimized RR materials for building application by investigating and comparing their performance. A base ceramic tile has been coated with glass beads: glass spheres (Glass) and clear solid barium titanate spheres (Barium). The experimental characterization showed that the base and the glass tile have a comparable global reflectance (30% and 32% respectively). The barium tile has a higher global reflectance, equal to 39%. Furthermore, the directional characterization showed that both the glass and the barium tiles have very strong retro-reflective properties. Moreover, the colorimetric analysis showed that the appearance of the base tile is kept almost unchanged when glass spheres are applied on it. A more evident change is observed when barium spheres are considered. Finally, the numerical simulations showed that the optimized RR materials applied on building envelope can increase the radiation energy reflected outwards the urban canyon up to 5% with respect to base materials, thus reducing the energy trapped within the urban canopy and thus the UHI effect at different latitudes.