Optimized Cool Coatings as a Strategy to Improve Urban Equivalent Albedo at Various Latitudes

This research study aimed to investigate the influences of angular-selective retro-reflective (AS-RR) and retro-reflective (RR) materials on the urban equivalent albedo (aeq). Full ray tracing solar analyses were conducted through the Monte Carlo-based numerical model validated in a previous work. Different geometry scenarios with different patterns of urban density were modelled. AS-RR and RR materials were alternately applied to the street and to the most irradiated façade. AS-RR materials were proposed to enhance the aeq of the urban environment particularly during summer. Solar analyses were reiterated for three latitudes (i.e., Oslo, Milan, Cairo). RR pavements and façades were capable of increasing the aeq throughout the year. However, implementing an angular-selective behavior allowed for a reduction of the mitigation potential of RR materials during the winter season. In their best application, RR and AS-RR materials enabled higher aeq in summer (122%) with negligible effects during the winter (7%). Finally, the study highlighted the need for exploiting numerical models capable of conducting full ray tracing solar analyses when investigating materials whose optical properties depend on the angle of incidence of the sunrays (such as RR materials).