Reducing outdoor air temperature, improving thermal comfort, and saving buildings' cooling energy demand in arid cities - Cool paving utilization

Cairo experiences extremely high temperatures, which increase buildings' cooling energy demand. Previous studies found that vegetation raises air temperature in low-density urban areas and has a weak effect on air temperature reduction in high-density urban areas in Cairo. Therefore, this study seeks to investigate the impact of cool paving, as an alternative strategy, on air temperature and buildings' energy demand reduction in urban areas of different densities. Three built-up areas with varying densities of 25 %, 50 %, and 85 % were selected and simulated by using ENVI-met to evaluate the effect of cool paving on air temperature reduction. Then, DesignBuilder model was used to calculate buildings' cooling energy savings resulting from air temperature reduction. This study showed that cool paving can reduce air temperature and buildings' cooling energy in 25 %, 50 %, and 85 % urban densities by 0.5 K - 2.5 %, 0.2 K - 1.4 %, and 0.1 K - 0.2 %, respectively. However, cool paving raised Physiological Equivalent Temperature (PET) in the three areas. Therefore, other scenarios combining vegetation and cool paving are discussed as possible solutions for the dilemma between air temperature and PET reduction. Combining trees with cool paving achieved this balance in the low-density urban area besides reducing cooling energy by 3.2 %.