An investigation towards the optimum design of retro-reflective materials as building envelopes for the enhancement of optical performance

Retro-reflective (RR) materials may represent an advanced solution for building envelopes, as they could contribute to Urban Heat Island mitigation. This study could bring novelty to the current state of the art on this topic, as it proposes to investigate the optimum design of glass beads RR materials for building application. To this aim, the impact of glass beads superficial density and diameter on the optical performance of RR materials has been further explored. In particular, 15 RR glass beads samples were developed, using a highly reflective paint as substrate and varying both glass beads superficial density and diameter. Also a diffusive sample, without RR glass beads, was made for comparison. Three different glass beads superficial density ranges and five diameter ranges were investigated. Samples were tested through spectrophotometric and angular reflection distribution analysis. All RR samples exhibited an overall lower solar reflectance compared to the diffusive sample, whereas RR samples with 200 ÷ 300 μm diameter exhibited the highest RR capability. By reducing glass beads superficial density, generally a reduction of RR performance was observed.