Creation of low or zero-carbon neighbourhoods

The Accounting for carbon in planning residential neighbourhoods project, undertaken with the Department of Transport and Major Infrastructure, Western Australian Planning Commission, Department of Planning, Lands, and Heritage, and the University of Western Australia has been completed, and below is a summary of the project’s objectives and outcomes.

In a world racing to reach Net Zero, how we design our neighbourhoods could be just as important as the technology we put in them. This project set out with the aim to transform the way we think about housing, streets, and entire communities so that they actively avoid carbon emissions, rather than add to them.

Objectives

At its heart, this research had four main aims:

1. Designing for low or zero carbon: Explore how new greenfield developments and densifying existing neighbourhoods can be planned and built to avoid carbon emissions, moving us toward communities that are low or even zero-carbon.
2. Pinpointing the main culprits: Identify the biggest sources of greenhouse gas emissions in neighbourhoods, from how streets and parks are laid out to the types of homes we build, and uncover how smart planning and design can shrink them.
3. Integrating carbon into planning stages: Work out how to model and report emissions at the earliest stages of planning during district and local structure plans and ensure those commitments flow through into actual development.
4. Creating clear, measurable indicators: Develop practical indicators and assessment methods that planners can use to track and verify emissions performance in residential areas.

Report findings

Phase 1

The Phase 1 report analysed the emissions associated with land clearing, subdivision works, built form (embodied and operational), transport, and water in five case study precincts, i.e. three urban-edge greenfield (Jindalee, Southern River and Ellenbrook) and two urban infill (Nollamara and Subi Centro) as nominated by the Department of Planning Lands and Heritage working group. The case studies were selected to represent contemporary development patterns, so findings are ‘generalisable’ to structure plan areas in the future.

Analysis of cumulative 50-year precinct emissions per dwelling reveals that the infill case studies Nollamara and Subiaco have the lowest emissions, and the greenfield case studies Ellenbrook and Southern River have the highest emissions, followed by Jindalee.

The differences between the precinct emissions per dwelling can be summarised as follows.

Subdivision works:

• Development in lower-lying areas (e.g., Southern River and Ellenbrook) leads to significantly higher emissions than the other greenfield precinct (Jindalee) due to the requirements for fill (and, in many cases, sub-soil drainage).
• Avoiding subdivision works in infill precincts (e.g. Subiaco, Nollamara) essentially eliminates this source of emissions.

Built form:

• The precincts with smaller built-form Gross Floor Areas (GFAs) have lower embodied energy / emissions in the built-form (e.g., Nollamara or Subiaco).
• The background infill and Transit Oriented Development precincts (Nollamara and Subiaco, respectively) have lower built-form embodied emissions than the greenfield compact suburbs (e.g., Southern River and Ellenbrook).
• Higher-density areas (Subiaco) can still have comparatively high operational emissions compared to lower-density background infill and even some examples of compact suburbs (e.g., Jindalee or Southern River).

Transport emissions (private cars):

• The private car emissions are roughly correlated with increasing distance to the Perth CBD for the precincts. Subiaco has the dual advantage of being close to the CBD and having local jobs and services, resulting in the lowest transport emissions.

Vegetation-related emissions

• The relative impact of land clearing and landscaping on emissions, while important, is minor compared to other categories across the precincts.

Water and wastewater-related emissions

• The indirect emissions associated with water and wastewater are minor compared to other emissions sources. Nonetheless, the suburban precinct with larger lots (Ellenbrook) had higher water use than the compact suburb and infill precincts (e.g., Jindalee or Nollamara).

Phase 2

The Phase 2 report evaluated interventions that can avoid future emissions. These interventions were identified through a literature review, demographic analysis, and a workshop with the Department of Planning Lands and Heritage staff and the Accounting for Carbon working group.

Subsequently, the impacts of the interventions were quantified and incorporated into a system dynamics model to calculate per-dwelling life-cycle emissions across our five precinct case studies. The interventions in each case study were modelled from a baseline year when the corresponding Structure Plan was approved (e.g., for Subi Centro, this was 1994).

Planning and design interventions that can reduce emissions include:

• Avoidance of development in shallow groundwater sites;
• Reduction in fill for such sites that are developed;
• Re-configuration of dwelling types and sizes to better reflect the population’s existing and likely future demographics;
• Smaller dwellings to deliver more private open space to facilitate trees and gardens; and
• Optimised solar access for rooftop solar PVand winter passive heating.

These planning and design interventions would result in:

• Lower levels of embodied carbon in both the subdivision works and the built-form; and
• Lower operational energy demand.

These measures can reduce lifecycle per dwelling energy supply and transport emissions by 30-50%.

Home electrification interventions that can reduce emissions include:

• Replacing the use of gas in homes, e.g. with heat-pump water heaters and electric stovetops.
• Take-up of electric vehicles; both in tandem with; and
• Increasing penetration of rooftop solar PV and home batteries.

Together with planning and design measures, these measures will potentially reduce lifecycle per dwelling energy supply and transport emissions by a further 30-35%.

Embodied emissions can be reduced by using alternative forms of construction, including:

• Incorporation of cement replacement materials in concrete; and
• Sustainably produced timber products for framing and wall cladding.

These measures lead to significant reductions in embodied emissions of around 50% per square metre of GFA. Across the interventions, the potential reduction in emissions per dwelling is lower in the infill development sites as dwelling sizes are already smaller and densities are already higher than in the greenfield sites – nonetheless, the reductions are still significant.

Of the intervention categories, those that relate to planning and design (e.g., urban density and layout) and home electrification (e.g., purchasing household batteries) typically have the most significant impact on emissions.

Modelling shows that re-configuring dwelling types and sizes to reflect better the existing and likely future demographics is critical to reducing emissions and offering other benefits. From a developer perspective, this would lead to a larger number and greater diversity of lots per hectare of development. From a builder’s perspective, this would lead to more dwelling completions per square metre of constructed built form.

Phase 3

The Phase 3 report identified changes within the planning and design system that contribute to low- or zero-carbon neighbourhoods. It is recommended that the State Planning Strategy 2050 and planning policies be reviewed and revised to reflect the importance of climate change to the various regions of Western Australia and align the planning system with governmental climate change legislation regarding Net Zero emissions and adaption to climate change.

This review would also include consideration of the following:

• The region scheme Amendment Reports include a section on climate change, including the influence of location on greenhouse gas emissions.
• Structure planning to be required to incorporate analysis of the micro-climatic performance of the fully developed precinct.
• The Energy and Greenhouse Gas Statement to require an evaluation of life-cycle emissions associated with the fully developed precinct.
• Subdivision works approvals requiring measures to be taken to minimise earthworks and drainage infrastructure and emissions associated with transport and construction vehicles.
• The Department of Energy, Mines, Industry Regulation and Safety review the NSW BASIX scheme’s application of a Materials Index to require a similar calculation of embodied energy to be submitted with building permit applications.
• The Department of Energy, Mines, Industry Regulation and Safety review the progress of the Victorian scheme to introduce a similar ban on gas connections in new premises through the building permit process.
• A future review of Perth & Peel @ 3.5 million to analyse alternative development scenarios for Greater Perth that fully account for climate change. This review could also reconsider Perth’s infill target of 47%.

Conclusions and recommendations

This work confirms eRideables have a growing role in urban mobility. Their benefits as a transport mode include enjoyment, convenience, cost effectiveness and low environmental impact.

People who use eRideables value the mode for short (<8 km) door-to-door trips and enjoy how they provide freedom and flexibility, removing the need to drive on congested roads.

There are however challenges to address if eRideables are to fully contribute to  sustainable mobility in Perth.

The research team recommended action to:

• Further engage with eRideable users about their experiences
• Educate for safe use of eRideables and encourage mutual consideration amongst all modes
• Improve infrastructure to accommodate eRideables while reducing safety issues
• Develop policy and regulatory response to evolving eRideable technology and use patterns.

For eRideables to meet their full potential, a coordinated, multi-disciplinary approach is needed to promote equity, inclusion and safety.

Expected project impacts

The research outcomes provide valuable inputs into the work the Department of Planning, Lands and Heritage undertakes on behalf of the Western Australian Planning Commission to enhance the planning system’s responsiveness to climate change. In particular, this research provides new insights to inform ongoing planning policy reviews that consider the decarbonisation of the built environment in Western Australia, as well as adaptation to the increasing frequency and intensity of extreme weather and natural hazards associated with climate change.

Department of Planning, Lands and Heritage

Download the report

Download your copy of the final report, Accounting for carbon in the planning for residential neighbourhoods – Final report: Summary and recommendations, by clicking the button below.

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