Green roofs to reduce building energy use? A review on key structural factors of green roofs and their effects on urban climate

In the next decades, the increase in global population will lead to further urbanization determining, on the one hand, an increase in building energy use and, on the other hand, a surge in urban temperature, which, in turn, affects building energy demand. Since the building sector greatly contributes to the use of energy globally, the amelioration of this sector is an urgent issue to contribute to climate stabilization. Published literature shows that green roofs affect both directly and indirectly building energy use, delivering the message that green roofs are fit-all solutions. However, the efficacy of the deployment of green roofs varies depending on climate and on their specific design. The present study contains a geographically explicit review of the potential building energy benefits deriving by the installation of green roofs depending on their specific design aiming at answering to the following research questions: - Are green roofs fit-all solutions for decreasing building energy use in diverse climates? - How insulation, growing media, and plant selection of green roofs should be calibrated in different climates to maximize their effect on building energy use? - How green roofs can contribute to urban heat island-mitigation in different climates? Answering these research-questions, this study provides urban decision-makers and planning agencies useful insights to, not only prioritize strategies, but also efficiently design by-laws and local regulations to maximize the potential positive effect of urban-wide green roof deployment on building energy use.