Urban canopy shading: opportunities to reduce cooling requirements

Abstract

As a result of the current economic and energy crisis, it has become necessary to rethink urban planning, starting from a global concept of efficiency and considering buildings not as isolated entities, but as part of an urban system, which consumes energy on a much larger scale. The connection between urban morphology and microclimate is a widely discussed question, including issues like the urban heat island phenomenon or outdoor comfort in open spaces. However, there is still a lot of work to be done regarding the influence of these microclimatic variations on building energy consumption. In that sense, would it be possible to apply efficient measures of microclimate modification on an urban scale to increase comfort levels in public spaces while at the same time, reducing building consumption? This paper focuses on urban canopy shading. Its effectiveness as a shading device and its capability to improve outdoor climate in areas with an excess of solar radiation is widely demonstrated. In this case, its effect on indoor climate of is evaluated. The case study is located in Cordoba (Spain), as an example of a climate with a hot and dry summer (according to CTE, level 4). A complete street canyon model has been created. Two buildings, one on each side of the street canyon, have been tested using an energy simulation software (Design Builder). Model features and simulation settings correspond to real values. Urban canopy shading effectiveness has been analyzed according to cooling demand decrease, taking into account both buildings. Spatial factors (street orientation, width-height ratio, windows-opaque ratio) and material factors (U-values and skin mass, % obstruction) have been considered. Results show 18% to 45% cooling demand decrease due to the canopy shading. Spatial factors are much more relevant than material factors: windows-opaque ratio is a determining factor, in contrast to mass and U-values. This study shows the importance of evaluating both urban facades, which means working from an urban perspective beyond the local scale of a single building.