Multi-level numerical and statistical analysis of the hygrothermal behavior of a non-vegetated green roof in a mediterranean climate

Green Roofs (GR) represent a sustainable technological solution for reducing the environmental footprint ofurban areas. Despite their benefits, traditional GRs have been criticized regarding their economic feasibility,suggesting to develop advanced hybrid engineering solutions able to simultaneously maximize their hydrologicaland energetic benefits. In this view, there is a need of numerical models able to describe their complete hy-grothermal behavior. Thus, the main aim of this study was to assess the suitability of the one-dimensionalmechanistic model HYDRUS-1D in providing an accurate and comprehensive description of the coupled water-heat-vapor transport in afield-scale Non-Vegetated Green Roof (NVGR) in the south of Italy. A complete cali-bration framework, which encompassed the Particle Swarm Optimization (PSO) algorithm and the combinedGlobal Sensitivity Analysis-Generalized Likelihood Uncertainty Estimation (GSA-GLUE) method, was used toestimate the substrate thermal properties and assess the model predictive uncertainty. The calibrated model wasexploited to examine the cooling efficiency of a combined Stormwater Reuse-NVGR system in the warm season.The analysis revealed that deeper substrates are positively correlated with thermal lag and attenuation, and thatthe irrigation can be properly designed to trigger the evaporative and convective cooling of the NVGR. TheResponse Surface methodology wasfinally used to optimize the watering regime on an 8 cm-deep NVGR. Theexploitation of the evaporative cooling effect of the NVGR by means of a model-based irrigation optimization ledto a reduction of the average soil bottom temperature of 4 °C. The coupled system was able to maximize theenergetic benefits of GR