Cool Pavements for Sustainable Urban Development

Around the world, urban development and densification leads to the Urban Heat Islands (UHI) effect, in which cities are warmer than adjoining rural areas. Cool pavements have been recommended as a mitigating strategy for the UHI effect. However, the spatial extent over which cool pavements need to be applied to achieve widespread mitigation has received little attention. A previously developed urban microclimatic model for the Power Ranch community in suburban Phoenix, Arizona, was used to investigate this question. The microclimatic model is used to investigate the effects of urban densification for the meteorological conditions at 5:00 PM on August 13, 2015. In the modeled scenario, the heights of the buildings were increased from 5 m to 10 m, a large, central park was redeveloped as a parking lot, and a reflective pavement was implemented in the parking lot. Both localized and downwind air temperature effects at 2m of this further densification were quantified in the modelling effort. For the lower building height, using typical concrete to redevelop the park as a parking lot increased the 2 m air temperature directly over and downstream by about 0.20℃. When a reflective concrete parking lot was used instead, the 2m air temperature decreased by 0.20℃ over and downstream. At 10 m building heights, the reflective parking lot decreased the 2 m air temperature by 0.20℃, however, its effect was more localized with less benefit for downstream areas. Thus, urban form with taller buildings affects the airflow, which requires a more distributed application of reflective surfaces to mitigate UHI.