Comparison of Parasol Heat Mitigation due to Differences in Fabric Color and Polyurethane Coating

Abstract

The objective of this study was to clarify the effect of parasol fabric color and polyurethane (PU) coating on reducing UTCI. The measurements were carried out from July 21 to 23, 2021 on a tennis court, lawn, and concrete surfaces at Daido University in Nagoya, Japan. The thermal parameters under four parasols including Parasol (silver), Parasol with PU (white), Parasol with PU (silver), and Parasol with PU (white + shading net), as well as in the sun as a reference, were measured. Following findings were obtained through the measurements. Among the parasols used in this study, the white parasol had the largest solar shading effect and the smallest increase in downward heat radiation caused by the rise in fabric temperature due to solar absorption. The MRT value under the parasols were affected by the radiation characteristics of the parasol fabrics (solar shading rate and downward heat radiation increase rate) and the ground surfaces (albedo and solar absorptance). On the tennis courts, the largest UTCI reduction was -3.6 °C for Parasol with PU (white + shading net), followed by -3.0 °C for Parasol with PU (white), -2.6 °C for Parasol with PU (silver), and -1.4 °C for Parasol (silver). The UTCI reduction of the white parasol was greater than that of silver one.