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

Alessia Di Giuseppe,Lucio Postrioti,Federico Rossi,Alberto Maria Gambelli,Mirko Filipponi,Beatrice Castellani,Marta Cardinali,Andrea Nicolini

doi:10.3390/en14102921

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.

Highlights

IntroductionCities are continuously suffering from several anthropizationrelated issues: human activities, generate high levels of air pollution, anthropogenic heat, energy consumptions, and greenhouse gases emissions, which contribute to the so-called Urban Heat Island (UHI) effect [1,2]
The present work aims at investigating the potential effect of a different substrate material on the optic performance of a RR coating, made of a high-reflective white paint with glass beads embedded on it
For an angle of incidence of −30◦, DIFFSA reveals a more symmetrical diffusive distribution, whereas the two wood-based diffusive samples, i.e., DIFFRW and DIFFSW, show a slight rightward shift of their reflectivity profiles, which means that a specular reflection occurs for low incident angles

Summary

Introduction

Cities are continuously suffering from several anthropizationrelated issues: human activities, generate high levels of air pollution, anthropogenic heat, energy consumptions, and greenhouse gases emissions, which contribute to the so-called Urban Heat Island (UHI) effect [1,2]. Such a phenomenon occurs with an increase in urban air temperatures with respect to the natural, not populated areas nearby [3].

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