Green Roofs in Buildings: Thermal and Environmental Behaviour

Although in many countries green roofs still appear to be a novelty, they are in fact a technology that has been known for centuries. During the past decade, urban policies and building regulations in many countries worldwide have led to an increase in the popularity of this technique, mostly due to the belief that green roofs play a key role in environmental restoration in areas where city growth has resulted in significant urban climate deterioration and an increase in the energy consumption of buildings. Until recently, the benefits of green roofs were more qualitative than quantitative in character and they were compared with the benefits of vegetation surfaces. During the past decade, a great number of studies in many different scientific fields have produced important knowledge concerning the actual performance of this green technology and have managed to quantify its performance through a mathematical or experimental approach. Recently, a number of computer models have been introduced that are expected to contribute more to our existing knowledge. The purpose of this study is to present the recent developments in green roof technology. This chapter focuses mainly on the contribution of green roofs to the energy consumption of buildings, but also reports the results of research relating to most of the other environmental benefits that are reported in literature.