Demonstrating the Use of Below-Substrate Water Storage as a Means of Maintaining Green Roofs—Performance Data and a Novel Approach to Achieve Public Understanding

Green roofs are becoming increasingly important in the challenge of dealing with climate change and urbanisation. One of the challenges for green roof design and construction is the need to trap large volumes of water on roof structures with limited load bearing capacity. If this is attempted by using increased volumes of mineral substrate the ratio of water volume stored to total load can be insufficient to achieve the water attenuation aims of the system within the limited load constraints. This paper reports on the performance aspects of the approach of closely integrating stormwater capture, storage and reuse within a green roof and reports some preliminary data which indicates the effectiveness of the capillary feeding device used to supply water from relatively deep void forming drainage, conveyance and water storage layer into the overlying substrate of a green roof. A case study is presented where a roof park is formed on the first floor deck of a former bus station and includes a modelling exercise to demonstrate the value of the stored water for maintaining the “urban roof park” environment. A unique demonstration project is also presented.