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

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.

Impact of Urban Vegetation on Outdoor Thermal Comfort: Comparison between a Mediterranean City (Lecce, Italy) and a Northern European City (Lahti, Finland)

“…For example, Taleghani et al [59] showed that the courtyard provides the most comfortable microclimate in the Netherlands in June compared to other urban forms. Lobaccaro et al [61], through a study in Bilbao, found that the orientation and aspect ratio strongly affected the magnitude and duration of the thermal peaks at pedestrian level, with the vegetation elements improving the thermal comfort. This suggests that there is not a general mitigation strategy using vegetation which could be applied for all scenarios, but ad hoc studies are necessary to optimize the benefits of introducing vegetation for thermal comfort improvement purposes [24][25][26].…”

Roof-Integrated Green Technologies, Energy Saving and Outdoor Thermal Comfort: Insights from a Case Study in Urban Environment

“…orientation and aspect ratio) significantly affect the intensity and duration of the thermal peaks; green urban infrastructures (i.e. green roofs and green surfaces) strongly improve the thermal comfort conditions and human health [22].…”

Evaluating the 3D cooling performances of different vegetation combinations in the urban area

“…A study in Hong Kong to evaluate the cooling performance of various tree species in different urban morphology has suggested that tall trees of low leaf area density (LAD) should be planted in deep canyons and vice-versa for shallow canyons and open-areas [28]. Nevertheless, a few studies have explored the cooling effects of plant combinations on the urban thermal environment [29,30].…”