Aylesford Project Smart Roof 2.1 - light case study
Where
When Polypipe’s offices in Aylesford, Kent, required roofing renovations, the decision to create a Blue-Green roof was an easy one, and provided the opportunity for the design and development of a new, intelligent water management system. The goal of the research was also to get an even better understanding of the functioning of blue-green roofs in the UK, supplemental to all knowledge already compiled at the parent roof in Amsterdam.
Recognising that the health and survival of a green roof can be dependent upon unpredictable weather patterns and require ongoing maintenance, we worked to create a system which automatically manages water supplies to provide optimum soil moisture conditions, allowing the green roof to flourish – maximising its benefits.
The Project SmartRoof 2.0 research project started in April 2017 and aimed at determining hydrological, thermal and biodiverse functioning of blue-green roof systems in the urban environment. The goal was to harvest and store as much rainwater for capillary plant irrigation as possible and use drinking water only in cases of extreme prolonged droughts.
The hypothesis was that plants in blue-green roof systems have a higher urban cooling capacity, can enable a wider plant species selection due to improved water availability, as well as reduce the precipitation lost to sewer discharge.
One plot was constructed like a conventional extensive green roof, equipped with a 25mm drainage mat and a 4cm substrate layer. The other two plots were equipped with an 85mm drainage, storage and capillary irrigation system, with water storage maximised (by overflow) to 30mm out of the available 80mm capacity (due to weight restrictions on the roof). One was covered with a 4cm substrate and the other with an 8cm substrate. Surface and air temperatures on an adjacent reference black bituminous roof were also monitored.
A complete array of sensors was installed to measure heat fluxes (incoming sunlight, reflected light, surface temperatures, soil and air temperatures). Weather data was gathered with an on-site weather station (rainfall, solar radiation, air temperature, relative humidity, wind speed and direction). A weighing lysimeter was built into each research area to determine actual plant evaporation in relation to time. Soil moisture and water levels in the units were monitored and recorded. A second temperature monitoring station was placed on an adjacent black roof.
After placement of sedum mix blankets, 40 plant species native to Europe were sown on the sedum carpet/substrate to increase the biodiversity and to give insight in the change in plant species distribution over time. All plots received the same initial vegetation and seed mix as well as the same maintenance and fertilisation regime throughout the entire research period.