The Effect of the Substrate on the Optic Performance of Retro-Reflective Coatings: An In-Lab Investigation

Abstract

Retro-reflectivity is a promising surface capability, which has attracted the interest of researchers for building applications in order to counteract Urban Heat Island (UHI) effects. This work aims at studying the impact of the substrate material on the optic performance of retro-reflective (RR) coatings. Three types of substrate materials were investigated: smooth pine wood panels, rough plywood panels, and smooth acetate sheets. The RR coating samples were made by firstly adding a high reflective white paint onto the substrate material and a homogeneous RR glass beads layer on the top. As a reference case, also diffusive samples, without RR beads, were developed. Samples have been tested through a spectrophotometric and an angular reflectivity analysis. Results show that, despite a lower global reflectance of the RR samples with respect to the diffusive ones, the glass beads coating provides a good retro-reflective capability to all the diffusive samples. Additionally, the roughest RR sample exhibited the highest RR capability of up to 16%, with respect to the other smoother samples. Future developments may involve the optimum design of RR coatings, in terms of their optic performance by varying the substrate materials and roughness, the glass beads density and dimension.

Glass beads retro-reflective coating for building application: albedo assessment in urban canyon configurations

“…Results from this previous contribution [10] showed that the glass beads modified the global reflectance of the high-reflective paint, but they provided a directional reflectance capability to the coating. It was demonstrated that the HR coating exhibited the highest global reflectance (80.1%), whereas for the RR coating it decreases to 72.8% [10]. Despite this lower global reflectance, the RR coating provides a strong retro-reflective component for incident directions near the normal to the surface (i.e.…”

“…the ratio between glass beads and white paint was 1:1). In a previous work [10], the optical performance of the abovementioned HR and RR coatings was analyzed in lab with both spectrophotometric and angular reflectivity characterization. Results from this previous contribution [10] showed that the glass beads modified the global reflectance of the high-reflective paint, but they provided a directional reflectance capability to the coating.…”

“…In a previous work [10], the optical performance of the abovementioned HR and RR coatings was analyzed in lab with both spectrophotometric and angular reflectivity characterization. Results from this previous contribution [10] showed that the glass beads modified the global reflectance of the high-reflective paint, but they provided a directional reflectance capability to the coating. It was demonstrated that the HR coating exhibited the highest global reflectance (80.1%), whereas for the RR coating it decreases to 72.8% [10].…”

“…Despite this lower global reflectance, the RR coating provides a strong retro-reflective component for incident directions near the normal to the surface (i.e. from 90° to -40°), with the maximum retro-reflective capability equal to 16.2% at 90° angle of incident radiation [10].…”

“…In the present work, the HR and RR coatings, whose optical features have already been assessed [10], are further investigated as coatings of an urban canyon facility. The canyon's vertical surfaces were firstly coated by the HR paint and then by the RR coating, applying them directly to the walls of the inner courtyard.…”