Optic-energy and visual comfort analysis of retro-reflective building plasters

This paper presents the results of the characterization of new retroreflective (RR) plasters for outdoor applications. The paint was obtained through deposition of four different types of RR microspheres on a traditional plaster for exterior applications. The plasters were characterized through a spectrophotometric, directional and colorimetric analysis. All the types of microspheres provide strong RR behavior for incident light directions from 0° to 60° with respect to the surface normal. However, the aluminum coating, with and without fluoropolymer coating, affects negatively the global reflectance and change completely the tiles’ original color, making the application of the aluminum RR tiles very limited. Glass and barium microspheres instead improve the optic properties of the original plaster, with negligible effects on the color. An analytic model was used to evaluate the amount of energy that is reflected beyond the canyon by the RR materials. It was found that at 42°N latitude, the best performing configurations are the combination of RR façade and RR pavement, for glass spheres. Two full-scale vertical surfaces, covered with RR plaster with glass microspheres and diffusive plaster respectively, were developed to investigate the visual comfort of pedestrians, in particular glare. Results show that the Daily Glare Probability (DGP) and superficial temperature for the RR wall is always lower than those for the diffusive wall.