Mitigating urban heat island effects in high-density cities based on sky view factor and urban morphological understanding: a study of Hong Kong

The urban heat island (UHI) effect is one of the most studied topics in many mega cities because of rapid urbanization. The literature review showed a significant correlation between sky view factor (SVF) and UHI. However, this climate knowledge has low impact on urban planning process to mitigate UHI. More studies should be devoted to ways of mitigating UHI based on an understanding of SVF and planning parameters. This article first evaluates the effect of SVF on UHI in urban areas of Hong Kong by a sensitivity analysis in SVF and the air temperature obtained from traverse measurements. Second, this article reports a parametric study to link SVF with site coverage ratio and building height as two practical planning parameters, assuming constant land use density. To predict the phenomenon better, a comparison analysis between real urban areas and parametric models further calibrates the SVF calculated in the parametric models. The study indicates that by carefully controlling site coverage ratio and building height, urban planners could effectively increase SVF to mitigate UHI in high-density urban areas without losing the development efficacy of the land.