News from the front desk: Australia’s urban municipalities have historically sought to boost tree canopy cover on public land to mitigate the built environment’s contribution to urban heat, increased air-conditioning use and higher electricity prices.
In a radical policy first for an Australian metropolis, the City of Melbourne announced last week plans to force developers to reverse the urban heat island effect by incorporating urban ecology solutions into new large residential and commercial buildings as part of its push towards net zero emissions.
A planned amendment to Victorian state planning legislation would require developers of buildings larger than 5000 square metres to use the City’s custom Green Factor tool to include green infrastructure such as green roofs and vertical gardens over at least 75 per cent of a total given site area.
The City is pushing the envelope further towards the private sector than any other Australian municipality to date, with rivals such as the City of Sydney reliant on boosting the number of street trees on public land to reach stated tree canopy targets outlined in its Greening Sydney strategy published in August 2021.
In contrast, Melbourne is leaning on private landholders to do much of the heavy lifting to increase the city’s green cover via green infrastructure, according to an explanatory statement the council released.
“Sustainable building design requires current generations to choose how they meet their needs without compromising the ability of future generations to be able to do the same,” the statement noted. “The City of Melbourne owns and controls less than one third of the municipality’s land area, with most of the land in private ownership or other government ownership.
“In terms of built form, City of Melbourne owns less than 2 per cent of the buildings in the municipality. Private development is therefore a critical contributor to any overarching municipal goals or targets.”
The proposed amendment to the Victorian Planning and Environment Act 1987 known as the Sustainable Building Design – Planning Scheme Amendment, spans policy, mandatory and optional planning controls.
Under the amendment, at least 75 per centof a development’s total site area must comprise building or landscape elements that reduce the impact of the urban heat island effect, which occurs when the presence of concrete and other hard surfaces absorb and retain heat and increase surrounding air temperatures, boosting demand for air-conditioning and contributing to spiralling energy costs.
It is the first time an Australian jurisdiction has specifically included the urban heat island effect in a planning instrument, according to a City of Melbourne spokesperson.
It is the first time an Australian jurisdiction has specifically included the urban heat island effect in a planning instrument, according to a City of Melbourne spokesperson.
Green infrastructure mitigates the urban heat island effect by deflecting radiant heat from the sun, shading building surfaces and releasing moisture into the atmosphere via evapotranspiration. Green roofs also absorb pollutants from surrounding areas.
The built environment contributes 66 per cent of Melbourne’s greenhouse gas emissions. Energy efficiency and embodied carbon measures will go towards helping the City achieve its stated net zero emissions target by 2040. If enacted, the new rules will also apply to additions of more than 1000 sq m to existing buildings.
As well as urban heat mitigation, buildings must achieve a minimum 50 per cent Built Environment Sustainability Scorecard (BESS) score while aiming for a 70 per cent score and consider new planning policies spanning biodiversity, sustainable development, transport and water sensitive urban design. Waste and resource recovery facilities must meet City of Melbourne guidelines or a precinct waste management plan.
If adopted, the new planning scheme will also require developers to provide bicycle, motorcycle and share parking, and electric vehicle infrastructure.
What Sydney is doing
For its part, the City of Sydney established new net zero targets for development approvals at a council meeting last August.
Development applications for new commercial buildings including hotels, offices and shopping centres, plus major redevelopments of existing buildings, must comply with minimum energy ratings from January 2023 and achieve net-zero energy use from 2026.
The policy relies on energy efficiency and the use of on-site and off-site renewable energy to help buildings operate on a net zero basis to help the City reach its overall net zero emissions by 2035 target.
Separately to this, City of Sydney is targeting a 40 per cent increase in green cover across the LGA, with a minimum 27 per cent tree canopy comprising trees of more than three metres tall by 2050. Currently, 20 per cent of all green cover is on private property, and under the strategy this will increase to 28 per cent by 2050.
Green cover in streets and parks will continue to contribute the lion’s share of the green area under the policy.
Melbourne’s use of urban ecology solutions is a departure to Sydney’s reliance on building performance standards through energy efficiency and renewable energy.
City of Melbourne is accepting submissions to the amendment until April 17 via the Participate Melbourne website. Ultimately, it is up to Victorian planning Minister Sonia Kilkenny whether to adopt the amendment or any proposed changes from the developer community, given that it concerns state government legislation.
Relying on the private sector to green the city makes good policy sense, given that private firms control most of the land and built environment in an urban area. One shortcoming of the Sydney and Melbourne policies is that they don’t affect privately-owned existing buildingsunless they are being redeveloped. In this respect, the City of Sydney’s Greening Sydney policies will touch on more existing buildings.
Melbourne’s policy direction echoes that of the City of London, which urges developers to consider green wall design incorporating vegetation of most of a building’s vertical surfaces in new developments. The Sustainable Design and Construction SPG also includes guidance on energy efficient design, CO2 reduction targets, urban greening and climate resilience.