Evaluation of Heat Stress Mitigation Effects of UV Parasols through UTCI Observations and Thermal Sensory Questionnaire Survey

Pedestrians in urban environments are highly susceptible to heat stress, primarily due to intense solar radiation while walking through open spaces. UV parasols are anticipated to serve as a personal method for mitigating heat stress, owing to their portability and ease of use in pedestrian settings. Thorough validation of their effectiveness in mitigating heat stress requires participant experiments that simulate real pedestrian experiences. We conducted meteorological observations and thermal sensory questionnaires to verify the effect of UV parasols in mitigating heat stress among urban pedestrians. To emphasize the distinctive features of UV parasols, we contrasted their effects with those of street trees, which provide fixed shading in urban walking areas. What distinguishes this study is the verification and comparison of the heat stress mitigation effects of UV parasols and street trees through participant experiments, specifically from the perspective of pedestrian comfort. The meteorological observation findings demonstrated that UV parasols decreased the Universal Thermal Climate Index (UTCI) by 3.6 °C compared to direct sunlight, equivalent to approximately 56 % of the reduction achieved by street trees. However, results from the thermal sensory questionnaire survey indicated that the alleviation of heat sensation by UV parasols was only approximately 30 % of that provided by street trees. This limited effectiveness of UV parasols is primarily ascribed to their inability to adequately shield pedestrians' entire bodies from solar radiation while in motion. The experimental outcomes obtained in this study are expected to contribute to the reduction of heat stroke incidents among urban pedestrians and the design of adaptation measures for climate change in pedestrian-centric urban planning.