Innovative green roof technologies in Mediterranean climate: Implications for sustainable design of the built environment

Abstract

Green roofs are increasingly recognized for their contributions to urban sustainability, offering benefits such as thermal regulation, stormwater management, energy efficiency, improved air quality, and enhanced biodiversity. However, the performance of green roofs in Mediterranean climates remains underexplored. This study evaluates the effectiveness of three distinct green roof technologies—Experimental, Draining Modules, and Green Safe—in Mediterranean conditions, focusing on thermal regulation, water retention, and energy savings. High-precision instruments, including thermocouples, heat flux sensors, and Time Domain Reflectometry (TDR) probes, were deployed to monitor performance over an eight-day summer period. The Experimental Technology, integrating biochar into the substrate, achieved the best thermal performance, with a surface temperature reduction of up to 9.8 °C compared to the reference roof, an average daily cooling energy savings of 3.8 kWh, and a total energy savings of 10 % over the simulation period. The Draining Modules Technology demonstrated moderate performance, with a surface temperature reduction of 6.5 °C and a total energy savings of 6.5 %, equating to 2.5 kWh of daily cooling energy savings. In contrast, the Green Safe Technology exhibited the highest surface temperatures and the lowest water retention, resulting in a surface temperature reduction of 5 °C and energy savings of only 5 % (equivalent to 1.9 kWh of daily energy savings). These findings underscore the potential of biochar-enhanced substrates in mitigating the Urban Heat Island (UHI) effect, reducing cooling energy demand, and improving building energy efficiency. This research provides quantitative insights for urban planners, architects, and policymakers seeking to implement more effective and sustainable green roof designs in regions with challenging climatic conditions, thereby supporting urban resilience and climate adaptation.