Influence of the thermal environment of urban sidewalks under green shading from a human scale

Abstract

ABSTRACTUrban footpaths are the main outdoor activity spaces for pedestrians. It is traditionally believed that the air temperature of a pedestrian walkway under tree shade is lower. However, from the perspective of vertical air temperature profiles, there is little difference in air temperatures between a shaded pedestrian walkway and one under unshaded sunlight. This paper adopts a human-centred approach to investigate the three-dimensional spatial distribution of air temperatures in a pedestrian walkway in Taipei City under tree shade. It analyzes the air temperature reduction caused by attenuation of ground reflected long-wave radiation due to shade, and the effect of shade on environmental ventilation. It was found that air temperatures varied along pedestrian walkway height and direction. The measured data shows that the main difference in air temperature between shaded areas and areas exposed to sunlight is in the 0–0.5 m height range, and there is little difference in air temperature between the 0.5 m-2 m height range.Higher shades led to poorer ventilation and were more likely to cause local overheating. This suggests the need to assess urban pedestrian thermal comfort from a three-dimensional perspective, considering not just planar shades but also vertical shading and ventilation.

Keywords

• Urban street canyons
• pedestrian walkways
• thermal images
• spatial dynamic probes
• Kriging