Green Guru
1 April 2015
Director Greg Yeoman is Stormwater360's greenroof designer and runs the green infrastructure programme, which includes LiveRoof (the modular greenroof system) and the Urban Green Biofilter.
Greg is one of the original visionaries of Stormwater360 and has a Bachelor of Architecture degree with a design background. He brings an understanding of space, texture, colour and contrast to all of the greenroofs he designs.
He shares his views on what makes a good greenroof.
- Function – The first consideration for any greenroof should be ‘what is the function of this greenroof?’
This will determine many factors such as; type of vegetation, depth of substrate (growing media), weight and slope considerations, acoustic and thermal requirements and stormwater management properties amongst other things. Greenroofs can also be used to offset the impermeable building area on a site, meaning that there is a possibility to have greater land coverage with your building.
- Growing media – Growing media is the heart of any greenroof. Extensive greenroofs are not simply elevated landscapes, but are engineered systems grown in very exposed environments. A successful growing media needs to be able to sustain plant life, but discourage growth of weeds and unwanted vegetation. It also needs to be able to capture and retain moisture for plants to draw upon later to survive. Growing media should have a low organic content and should have sufficient structure that it doesn’t compact over time. Growing media has a large effect on the overall weight of the greenroof, and should be evaluated both as dry and wet vegetated weights when considering loading implications. Lightweight materials such as pumice have high water holding capacity but are also lightweight, so are an ideal ingredient.
- Plants – Appropriate vegetation is essential for short and long-term survival of a greenroof. Many things need to be considered when evaluating the vegetation, such as; aesthetics (what do I want this greenroof to look like both short and long term?), maintenance considerations and on-going maintenance budget, irrigation and water budget (do I want the vegetation to absorb and process a lot of water for stormwater management or to conserve water to minimise irrigation requirements?) Native vs. non-native or succulent plant varieties (or a combination), Biodiversity (am I trying to attract any specific insects, birds or other animals to the greenroof habitat?)
- Drainage – It is essential that the drainage allowing water to drain through and away from any greenroof be well thought out. Any drainage mechanism needs to work both short term and long term over the life of the greenroof. If drainage fails, or water is held on the roof surface for any period of time, plants will become unhealthy and ponding will cause additional loading on the roof structure, which could lead to failure. Thought should be given to both drainage through the greenroof growing media as well as egress along the perimeter allowing water to flow to the building downpipes. If filter fabric is used in the greenroof system, there is potential it may get blocked from fines over time and become impermeable.
- Access – Access to the roof for both installation of the greenroof and on-going maintenance is often overlooked during the design phase and can have costly implications. Health and Safety while working at heights needs to be well considered by the architect and greenroof designer and any anchor points and /or static lines and access for maintenance activities need to be included in the budget.
- Design – A well-designed greenroof can incorporate all of the above and become a functional piece of art that gives your building added value and ongoing savings as well as improving your living environment and others around you. Colours, patterns, curves and textures can all be designed into your greenroof with the right design knowledge and plant selection.
For more information please contact Greg Yeoman:
