The effect of solar radiation on pedestrian thermal comfort: A climate chamber experiment

Walking promotes human health and well-being. However, increasing temperatures due to global climate change and urban heat islands challenge urban walkability. While people navigate urban settings, they encounter asymmetrical environmental conditions not captured by most thermal comfort models. Critically, these models predominantly factor in the Mean Radiant Temperature (MRT) but tend to neglect the effects of non-uniform solar radiation on human comfort. This study delves into the thermal impacts of solar radiation on walking individuals, utilizing a controlled environment with solar simulators. 28 subjects walked on a treadmill, simulating the walking state of pedestrians, under asymmetrical radiation conditions with the source being overhead, in front, behind, and to the side. Participants responded to queries concerning their overall thermal comfort, thermal sensation, and thermal acceptability. In addition, they provided feedback on directional and segmental thermal sensations across various body parts. Our findings revealed that the thermal sensation varied depending on the direction of radiation, and their responses regarding their forearms were most closely related to their whole body. These results provide information that can be valuable in the design of outdoor environments that will be thermally comfortable and will encourage people to walk during hot weather.