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Green Roofs for Australia Conference


Green Roofs for Australia Conference

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									Green Roofs for Australia Conference
Written by Stephanie Skyring, AGDF Sustainability Consultant

Green Roofs for Australia Conference
Brisbane Technology Park
February 22nd and 23rd 2007

The Green Roofs for Australia conference, held over two days in Brisbane in late February, was a
very welcome introduction to the processes and technicalities of addressing vegetation and
biodiversity in building design. The event was very well supported by Council, with the proceedings
being opened by Lord Mayor Campbell Newman and attended by a number of councillors including
Helen Abrahams, Judy Magub, Geraldine Knapp and David Hinchliffe. The federal Member for
Moreton the Honorable Gary Hardgrave also attended and opened the proceedings on day two,
demonstrating support at federal level for furthering development, training and implementation of
green roofs in Australia.

Green roofs have been common practice in northern Europe throughout history (sod roofs) and are
now widely accepted and encouraged as a part of contemporary building design in Europe and North
America. However, while Australia has a number of high profile examples of green roofed buildings
such as Parliament House in Canberra, the greater majority of Australian building developers and
design professionals are still hesitant.

The conference addressed an extensive range of issues with experienced speakers providing
information on the key elements such as construction and waterproofing concerns and plant
selection and maintenance. It also outlined the barriers that are slowing the progress of the green
roof industry development and provided some solutions for how to overcome them.

Steven Peck, the Founder and President of Green Roofs for Healthy Cities in North America was a
keynote speaker. He presented the well founded case that if the development industry is to remain
viable and become truly sustainable, buildings need to stop consuming resources and damaging the
environment and must provide a net positive benefit. It is essential they:
     • Be competitive to build and operate
     • Manage and clean water
     • Generate clean green energy
     • Conserve resources
     • Restore biodiversity
     • Provide healthy indoor and outdoor environments

The integration of green roofs and green walls into building design is an essential component of this
Green Roof Construction
The technicalities of constructing green roofs and green walls was discussed in detail, and a few of the
key items are as follows:

There are three types of green roofs which are defined from each other by a number of criteria,
however for simplicity of explanation they are:
    • Extensive (shallow planting medium – 150mm or less)
    • Semi-intensive (moderately deep planting medium – 25% above or below 150mm)
    • Intensive (deep planting medium – greater than 150mm eg. Deep planting for trees.

Three types of green walls:
    • Green facades – pots with vines on trellises located up walls
    • Active – soil / soil medium running up wall
    • Passive – epiphytes

Quite obviously, the two critical elements of successful green roofs are that they can’t leak and the
plant health must be maintained for the long term. Surprisingly, keeping the plants alive is actually the
more difficult of the two.

Longevity of the structure, drainage and waterproofing system is essential because the cost of
replacement is very high. Green roofs must (and can be) designed to last a minimum of 50 years.

The correct growing medium for the climate and plant selection is critical, particularly for extensive
roofs. The medium was comprised of a calculated ratio of aggregate (shale, vermiculite etc); organic
materials; air; and water. Standard soil was not usually used because it was too heavy.

Plant selection for green roofs requires very careful investigation and testing. Very different
conditions apply to vegetation on the roof compared to ground vegetation including wind, heat,
access for maintenance and drought and this needs to be carefully evaluated. Plants must suit the
harsh natural lighting conditions of roof tops and provide opportunities for biodiversity.

Long term plant maintenance is essential. A minimum 5 year maintenance contract is required to
ensure the correct processes are undertaken and plants get established.

There are now advanced examples of green roofs in Europe and the US that have been designed to
replicate natural ecosystems and processes:
      • A green roof of wild grasses on a building located in the prarie country of Winnipeg is
          burned off every 3 years to replicate natural regeneration processes.
      • The rocky gravel bird nesting habitat in disused quarry was reproduced on the roofs of a
          number of buildings adjoining the quarry area to enable birds to relocate prior to the
          subsequent quarry redevelopment.
This type of habitat replacement requires extensive research into what is required for the habitat to
make it authentic.

An interesting benefit of green roofs is their benefit to the efficiency of solar panels. Research has
clearly demonstrated that locating green roofs under solar panels optimises the effectiveness of the
solar panels. The green roofs provide a reduction in ambient temperatures increasing electrical

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Barriers to Green Roof Development
So what are the barriers?
    • Higher construction costs and no short term return on investment (Costs estimated at
         double the price of standard roof construction)
    • Technical data limitations in calculating benefits

Ways to bring down the costs of green roofs:
   • Integrate with design
   • Training (currently the experience of trades and professionals is very limited)
   • Research - Development of improved and more cost effective practices, products and
        materials (currently the most cost effective methods are achieved through increased scale)
   • Policy – it is preferable to lead with incentives rather than regulation.

Opportunities were raised for establishment of training courses in TAFE and universities, however it
was acknowledged that government and industry had to create and drive the demand for green roofs
to ensure that course participants had jobs to go to on completion.

Economic Advantages of Green Roofs:
While Australia has not yet properly recognised the financial benefits of building green, or green
roofs, overseas examples are setting the standard of what the future will hold.
In both North America and the UK green roofs are now synonymous with quality. Developers have
realised that buildings with green roofs will sell faster than standard roof designs, so they accept the
higher upfront costs because the return has been proven.

Particular development types also benefit directly from green roofs. Hotels and residential buildings
can gain direct financial advantage from green roofs when they are designed to incorporate communal
facilities such as pools, tennis courts etc.

Valuation of green buildings was addressed at the end of the conference and outlined key findings
from the US:
    • The additional costs of building green in the US is estimated to be 1-2%.
    • Most valuers like lenders are not up to date with green buildings.
    • Valuers keep using historical methods because lenders hold them accountable
    • Green buildings have an increased value of 10-15% above conventional buildings.
    • Green value is the net additional value obtainable by a green building in the market by
         reduced water consumption and reduced energy consumption.
    • The benefits of green buildings are gained by the tenants and the businesses located in the
    • The Appraisal Institute of America is currently creating new guidelines for valuing green
    • CB Richard Ellis International – Facilities Management Institute research has found that, “The
         annual costs of staff (wages etc) are equal to 85% of a building’s construction / design cost’
         Therefore upfront construction costs are therefore negligible compared to improving
         occupant productivity.

The speakers agreed that government had to lead with policy and incentives for green building
development. An example was presented from Basel, Switzerland where planning policy requires that
all new flat roofs must be green roofs.

While it was acknowledged that there are still a large number of barriers that need to be addressed
before green roofs can become a key part of Australian building design, there was strong support at a
political level and appreciation that this was the way forward for the future. The conference was
closed by Councillor David Hinchliffe with an affirmation of support from the BCC for the further
development and use of Green Roofs in Brisbane.

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