The Evolvement team have been conducting trials on a range of green roofs in our nursery. We are testing water management for runoff quantity and quality. The roofs provide horticultural monitoring of Australian native species and exotics suited to green roofs. Weight per M2 is another important factor we determine. Six different variations of green roof have been tested with different growing media and plants. Rainfall events and the resulting runoff data is collected and used to enhance our understanding of each system. Evolvement have worked with engineered growing media that provides both insulation and permanent growing conditions for a range of plants.
Green roof in Bondi with native plants providing water management and energy efficiencies.
Developers and architects in Australia are still hesitant to install green roofs as they are a load on the building and have potential to leak if not installed correctly. There is a general lack of understanding of how the system provides services. Compliance does however require developments to control peak discharge rates and provide energy savings. Evolvement now has relevant information on a range of systems to meet these requirements.
And THE WINNER IS! Plot number 3.
Plot number 3 weighs in at 45kg/M2. This is a fully saturated weight, few roofs will not be able to cope with this weight as a green roof system. The light weight and hence minimal materials required to provide for plantings also means considerable savings in installation and removal costs.
Evolvement green roof test panels showing rain gauge for monitoring precipitation. In May 2017 we received heavy falls. Our best plots provided a huge reduction in runoff and water quality was excellent. Peak discharge rates were remarkably reduced.
Plot number 3 retains 90% of most common rainfall events. This retention rate provides the ecosystem services common in bushland or forest areas, where water is absorbed into the ground and purified before it enters creeks and rivers.
Plot number 3 runoff is visibly clean and provides no gross pollutants and exceeds nutrient runoff requirements. We note that where only green roof soil media is used the water is visibly dirty after rain events even through a filter fabric.
Plot 2 used a quality engineered growing media and filter fabric only, this results in poor water quality and as you can see a large quantity of runoff after 25mm of rainfall.
Plot 3 incorporates is a synthetic growing media that is lightweight. As you can see after 25mm rain the plot only drained 250ml of clean water.
With the correct waterproofing and the addition of a leak detection system developers and architects need not worry about their building leaking. In fact there are many studies overseas that prove that green roofs will extend the life of waterproofing almost indefinitely and increase building life generally as roof temperatures remain static. Of course this temperature reduction reduces energy consumption considerably for your building.
Evolvement can design your next green roof system and its performance. Call Robert on 0468 787 071.