Thermal-energy analysis of natural "cool" stone aggregates as passive cooling and global warming mitigation technique

Recently, research focused on the development of roofing and paving systems aimed at (i) enhancing the passive cooling at single-building level and (ii) mitigating urban heat island at inter-building scale. In this work, the optic-thermal behavior of a naturally cool gravel for roof and paving application is studied, through lab and field experimental analyses. Specific evaluation about the cooling potential is carried out with varying grain size of the same gravel and stone typology. Additionally, its cool roof effect is investigated through dynamic simulation in a case study university campus in Italy. Finally, the analysis of the global warming contribution of the gravel was performed, with reference to the most performing gravel size. The results show differences up to 24% in terms of albedo with varying the only grain size. Additionally, the gravel with the smallest grain size resulted the most performing in terms of summer energy saving and indoor thermal comfort. By shifting from single building scale models to global climate energy balance models, an equivalent carbon emission offset of 4400 tCO2eq was found, imputable to the (i) energy saving contribution, and (ii) global warming mitigation effect produced by the enhanced albedo of the case study area.