Performance of Retro-Reflective Building Envelope Materials with Fixed Glass Beads

Jihui Yuan,Craig Farnham,Kazuo Emura

doi:10.3390/app9081714

Abstract

Urban heat islands (UHI) are growing in size and intensity, which is partly attributable to the large amount of anthropogenic waste heat. Moreover, heat emitted from building exterior walls accounts for a large portion of the total anthropogenic waste heat. Thus, strategies and technologies for preventing the emission of heat from building exterior walls are being pursued by researchers worldwide. Amongst these technologies, the potential of use of retro-reflective (RR) materials instead of diffuse highly reflective (HR) materials applied to building envelopes for UHI mitigation is being studied widely. However, RR materials haven’t been applied to building envelopes in practice due to their unproven weather resistance. In order to develop RR materials with high weather resistance for application to building envelopes, two types of micro glass beads with different refractive indices (1.5, 1.9) and five different colors of base layers were evaluated in this study. Their RR performance was measured by optical experiment and compared to two types of RR sheets commercially available in Japan. The results showed that the glass bead RR samples with a refractive index of 1.9 had much higher retro-reflectivity (better RR capacity) compared to those with a refractive index of 1.5.

Highlights

The urban heat island (UHI) phenomenon is a well-documented climatic change phenomenon in large cities worldwide [1,2]
The results showed that the glass bead RR samples with a refractive index of 1.9 had much higher retro-reflectivity compared to those with a refractive index of 1.5
In order to compare these developed glass bead RR samples to RR materials commercially available in the market, two types of RR materials were chosen in this study

Summary

Introduction

The urban heat island (UHI) phenomenon is a well-documented climatic change phenomenon in large cities worldwide [1,2]. The temperature differences between urban regions and surrounding rural regions are continuing to rise due to the UHI phenomenon and climate change [3], especially in the summer period. This might lead to an increase in building energy consumption during the summer period of cooling demand and affect the quality of human life [4,5]. Many strategies of mitigating UHI are being carried out globally. Among these strategies for UHI mitigation, highly reflective (HR) building envelopes are considered as one solution for UHI mitigation and building energy savings [6]. Research has indicated that HR materials could reduce the surface temperature of buildings, with peak drop up to 11.5 ◦ C [7]

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