Effects of Orientations, Aspect Ratios, Pavement Materials and Vegetation Elements on Thermal Stress inside Typical Urban Canyons

TLDR

Local climate analysis of artificial urban boundaries and their materials is essential for planning, as quantitative and qualitative studies show that finishing materials and sheltering objects influence microclimatic conditions and thermal comfort. The study aims to analyze summertime thermal stress in typical Bilbao urban canyons using Physiologically Equivalent Temperature computed with ENVI‑met. The authors modeled Bilbao’s urban canyons with varying orientations, height‑to‑width ratios, pavement materials (asphalt vs red brick), tree dimensions, and planting patterns, then compared current conditions, material effects, and vegetation benefits. Orientation and aspect ratio strongly influence the magnitude and duration of pedestrian‑level thermal peaks, while vegetation improves thermal comfort by up to two thermophysiological assessment classes, leading to green planning recommendations for Bilbao.

Abstract

The analysis of local climate conditions to test artificial urban boundaries and related climate hazards through modelling tools should become a common practice to inform public authorities about the benefits of planning alternatives. Different finishing materials and sheltering objects within urban canyons (UCs) can be tested, predicted and compared through quantitative and qualitative understanding of the relationships between the microclimatic environment and subjective thermal assessment. This process can work as support planning instrument in the early design phases as has been done in this study that aims to analyze the thermal stress within typical UCs of Bilbao (Spain) in summertime through the evaluation of Physiologically Equivalent Temperature using ENVI-met. The UCs are characterized by different orientations, height-to-width aspect ratios, pavement materials, trees’ dimensions and planting pattern. Firstly, the current situation was analyzed; secondly, the effects of asphalt and red brick stones as streets’ pavement materials were compared; thirdly, the benefits of vegetation elements were tested. The analysis demonstrated that orientation and aspect ratio strongly affect the magnitude and duration of the thermal peaks at pedestrian level; while the vegetation elements improve the thermal comfort up to two thermophysiological assessment classes. The outcomes of this study, were transferred and visualized into green planning recommendations for new and consolidated urban areas in Bilbao.