Street design and urban canyon solar access

Abstract

In his recent papers, Oke has challenged urban climatologists to establish quantitative and readily understood guidelines which might assist planners in the design of climatically rational cities, and has shown by example how such an approach might be taken for street canyon geometry. This study pursues Oke's arguments relating canyon structure to solar access within the canyon space using a numerical simulation methodology to explore the dependence of irradiance on the canyon facets, on a pedestrian within the canyon and the net irradiance at the canyon top on aspect ratio, street orientation, city latitude, season and sky condition. In addition, wall, floor and pedestrian ‘access indices’ are defined as the relevant irradiances divided by the equivalent horizontal surface, open-site solar irradiance, and it is suggested that such quantities, if presented in a form convenient to the planning practitioner, might constitute one type of parameter of use in an urban planning context.