Influence of Urban Design Interventions on Outdoor Thermal Comfort in Tropical Cities; a Review

Abstract

Comfortable urban environments attract people to public spaces. Urban designers have a great responsibility of creating thermally acceptable outdoors enhancing walkability and livability. Since intense urbanization has a harmful effect on OTC, experts tend to find strategies for urban discomfort, especially in tropics. However, transforming the current urban design into a climatic responsive design is challenging. Therefore, this paper reviews the influence of urban design interventions on OTC and concludes with the best strategies. The methodology includes two stages; bibliometric search and comprehensive content analysis which is limited to studies with physical and physiological assessments. Four components have been identified affecting OTC namely; urban surfaces, morphology, green, and blue infrastructure. Urban morphology is the most determinant component affecting OTC while green infrastructure is the most efficient method of improving comfort. Deeper canyons and compacted urban forms are more comfortable than shallow and aspersed forms. Hard surface coverage, urban form, prevailing wind conditions, morphological characteristics of tree species, and scale of open space available should be considered in vegetation inclusion. Since the material albedo and orientations of surfaces affect ambient air temperature increase, a high percentage of natural or artificial shading should be provided to adjacent hard surfaces and it helps to improve OTC irrespective of the surface material type. As a strategy, water bodies must be carefully considered in warm-humid climates and compacted urban areas. However, local climate, functionality, feasibility, and user perceptions must be considered and context-specific investigations are recommended using reliable methods such as CFD modeling prior to decision making.