Optical and thermal characterisation of cool asphalts to mitigate urban temperatures and building cooling demand

The Urban Heat Island (UHI) effect is defined as the increase of the urban air temperature compared to surrounding rural areas. The phenomenon is experienced at all latitudes and, combined with the global warming, has a severe impact at environment, energy and health level. The increasing of solar reflectance of urban materials is a strategy aimed at reducing surface and air temperatures and at mitigating the UHI. Cool materials applied to conventional asphalts are a viable technology for such purposes. The optical and thermal characterisation was carried out in laboratory and outdoor, and showed the enhanced properties and performances of several cool asphalt samples compared to conventional materials. The experimental data were used as input to simulate the thermal environment of a densely populated neighbourhood in Rome, estimating the effect of the roads albedo on the temperature air profile. Simulations performed with the software ENVI-met showed a significant reduction of air temperature closely correlated with the road solar reflectance. The air temperature profiles were used as input to calculate the impact of the albedo change at the building level. Simulations on the peak cooling demand of typical Italian dwellings were carried out by means of the TRNSYS dynamic simulation tool. Peak reductions of almost 19% were calculated for the highest solar reflectance configuration.

► Spectral reflectance and emissivity of cool asphalts were measured. Integrated values were calculated.
► Outdoor thermal monitoring of cool asphalts was carried out.
► The impact of cool asphalts on the mitigation of urban air temperatures was calculated.
► The impact of cool asphalts on the residential buildings' cooling peak demand was calculated.