Project title: Accounting for carbon in the planning for residential neighbourhoods
Milestone number: 2
Deliverable name: Interim Report: Model description, interventions, evaluation
Funding acknowledgment: This research is funded by iMOVE CRC and supported by the Cooperative Research Centres program, an Australian Government initiative.
Report authors: Bill Grace, Julian Bolleter, Chris Lund from the Australian Urban Design Research Centre (AUDRC)
Date: 14 01.25
Version: C
Executive summary
The overarching scope of the research is to identify the primary contributors to greenhouse gas emissions in predominately residential neighbourhoods. The purpose of this phase 2 report is to evaluate 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 perdwelling life-cycle emissions across our five precinct case studies. The greenfield case studies included Jindalee, Southern River and Ellenbrook, and our infill case studies included Nollamara and Subiaco.
Planning and design interventions that can avoid emissions include:
• the avoidance of development in shallow groundwater sites;
• a reduction in fill for such sites that are developed;
• the re-configuration of dwelling types and sizes to better reflect the population’s existing and likely future demographics;
• significantly higher gross dwelling densities to reduce need to travel and more private open space to facilitate trees and gardens; and
• optimised solar access for rooftop solar PV, summer thermal comfort and 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 potentially 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.
• the take-up of electric vehicles; both in tandem with
• increasing penetration of rooftop solar PV and home batteries
These measures, together with planning and design 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:
• the 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 m2 of Gross Floor Area. When combined with planning and design, and home electrification measures, life-cycle emissions would be reduced by a further 10-12% in houses and up to 20% in apartments. 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 sitesnonetheless, 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. Our modelling shows that re-configuring dwelling types and sizes to reflect better the existing and likely future demographics is critical to reducing emissions and offer 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 m2 of constructed built form. From a resident’s perspective it would lead to improved liveability, affordability and lower operational costs. In conclusion, our modelling reinforces a clear role for government policy and district and local structure planning efforts to yield low or zero-carbon neighbourhoods in Perth.
1. Introduction
1.1 Project description
The research considers the physical and social geography factors of new, predominantly residential neighbourhoods in metropolitan Perth and Peel and how planning and design impact the behaviour of residents and their associated greenhouse gas emissions, including factors affecting travel, transport and access to places of work, services and entertainment. The work will also inform planning and design in regional areas of Western Australia. The overarching scope of the research is to:
• Identify the primary contributors to greenhouse gas emissions in neighbourhoods and how emissions can be reduced through urban planning and design interventions related to subdivision patterns, street networks, open space systems, residential densities, building types, and environmental conditions.
• Determine how the modelling and reporting of emissions would occur at the district and local structure plan stages and how these could be followed through to implementation.
• Establish key indicators and assessment methodologies applicable at the district and local structure planning stages for residential areas.
• Examine how the design of new greenfield and existing densifying neighbourhoods can reduce carbon emissions and contribute to the creation of low or zero-carbon neighbourhoods
This report is the second of three research reports to be delivered:
• Phase 1 report: Case study area emissions;
• Phase 2 report: Model description, interventions, evaluation, and
• A final project report summarising the results of the research and recommendations.
The first phase of the research reported an assessment of life-cycle emissions in characteristic existing Perth metropolitan precincts, representing:
• conventional contemporary greenfield developments, and
• infill developments.
1.2 Project governance
The project steering committee comprises senior officers from the Departments of Transport (DoT), Planning Lands and Heritage (DPLH) and the iMOVE Cooperative Research Centre. DPLH has established a working group to guide the project.
1.3 Phase 1 report
1.3.1
The case study precincts
Phase 1 of the project reported on lifecycle greenhouse gas emissions for five case studies the DPLH Working Group selected
Table 1 The case study precincts
Case study Related planning document
Jindalee Jindalee NorthLocal Structure Plan 88 (2014)
Gosnells Southern River Precinct 3A Outline Development Plan (2009)
Ellenbrook Village 5- Ellenbrook City of Swan Development Plan (2001)
Subi Centro Subiaco Redevelopment Act 1994 1994 Transit Oriented Development Activity Centre policy (State Planning Policy 4.2) Precinct Design (State Planning Policy 7.2)
The analysis of development/ redevelopment within each precinct relates to a baseline year when the corresponding Structure Plan was approved.
1.4
Phase 2 scope
In this project phase, various interventions have been devised in conjunction with the DPLH Working Group and applied to each case study site. The selected interventions reflect the significant emissions sources identified in Phase 1. The interventions have been categorised as follows.
Table 2 Intervention categories
Planning and design Interventions under the control of planning and design through the planning system and built-form controls
Resident choice
Other government policies and market forces
Decisions that resident make about housing construction materials, home appliances, energy self-supply, transport modes and vehicles.
Government policy and/or market evolution related to:
• energy efficiency of built form and appliances;
• decarbonisation of the South West Interconnected System (SWIS);
• supply of natural gas to residential premises;
• the embodied emissions in construction materials.
The emissions associated with the interventions have been calculated and reported for each “reimagined” case study site.
1.5 Acknowledgements
The research team acknowledges the cooperation of several parties in providing information and support for the analysis presented here:
• Members of the project Steering Committee;
• Members of the DPLH Working Group;
• Officers of DPLH, DoT and DWER; and
• For the provision of data: Western Power, ATCO, Water Corporation and the local governments of Wanneroo, Gosnells, Stirling and Swan
Funding acknowledgment:
This research is funded by iMOVE CRC and supported by the Cooperative Research Centres program, an Australian Government initiative.
2. Methods
This section of the report summarises the methods for developing the interventions and calculating emissions sources. Further detail is provided in the following sections and the Appendices:
Appendix A Emissions intensities
Appendix B Building envelope emissions calculations
2.1 Identification of interventions
The identification of interventions was derived from numerous sources, including those proposed in:
• policy literature;
• planning literature, and
• a workshop with Department of Planning Lands and Heritage staff and project working group members (see Section 4.1.1)
Table 3 illustrates the intersection of the interventions with each emission source
Table 3 Identification of interventions
The potential interventions are set out by category in Figure 1.
2.2 Literature review
The review comprised studies of relevant literature related to a range of topics, namely:
• Urban design and planning;
• Development site works;
• Housing form and construction;
• Residential energy self-supply (i.e. solar PV and batteries) and
• Transition to electric vehicles (EV) and fuel efficiency in internal combustion engine vehicles (ICEV)
2.3 Data analysis
Data was collected from available sources, including via the literature review. Western Power provided additional data on residential electricity demand for the case study sites. The likely trajectory of emissions intensity for each of the emission sources was determined through this analysis.
2.4 Systems modelling
A system dynamics model of energy and emissions for each of the case study sites was developed to facilitate the evaluation of the impact of various interventions and their combination on lifecycle emissions.
Figure 1 Intervention categories
3. Interventions to reduce carbon emissions
3.1 Urban form and structure
This phase of work seeks to understand how emissions can be reduced through urban planning and design interventions related to road networks, open space systems, residential densities, building types, subdivision patterns and environmental conditions. These proposed design interventions were derived from the following:
• A ‘design intervention’ workshop was conducted with Department of Planning Lands and Heritage staff and project working group members (4.1.1);
• The related academic and policy literature on Green Urbanism, New Urbanism, Climate Sensitive Urban Design and solar passive design (4.1.2) and
• A demographic analysis of the mismatch between typically large houses and small average household sizes (Australian Bureau of Statistics, 2016) (see 4.1.3, Figure 2) to propose more compact average housing types within the case study precincts.
The interventions were also informed by the phase 1 findings, which identified the primary contributors to greenhouse gas emissions in dwellings and demographic analysis (e.g., household composition)
Figure 2: Methods for devising the case study interventions.
The design interventions related to these sources are discussed below.
3.1.1 The design intervention workshop
A design intervention workshop was conducted on 25.05.24 with 13 members of the Department of Planning Lands and Heritage and the Accounting for Carbon working group (Figure 3, Figure 4, Figure 5) Five groups were allocated one of the Phase 1 precinct case studies and asked to rate
different precinct configurations, street layouts, building types and open space structures for their potential to reduce energy use/ carbon emissions (Table 4).
There was consensus across the groups that a Transit Oriented Corridor Development (e.g. density along a corridor) precinct configuration would result in the lowest energy/ carbon emissions followed by Transit Oriented Node Development (e.g. density around a node)
There was a relative consensus that a Grid (150-250m street interval) street layout would result in the lowest energy/ carbon emissions followed by a Tight grid (150m street interval) or Super blocks (250m+ street interval)
There was general agreement that Perimeter block (2-6 storeys) building types would result in the lowest energy/ carbon emissions, followed by Slab (5-8 storeys, single loaded), Row house/ terrace (2-3 storey) and Semidetached (1-2 storey). Both Detached (1 storey) and Tower (> 10 storeys, double-loaded) rated very poorly, reflecting general support of medium-density building types.
A modest consensus was that a linear park design (e.g. Wungong) would result in the lowest energy/ carbon emissions, followed by a Single large park design (e.g. Hyde Park).
In summary, the workshop participants favoured neighbourhood designs that delivered medium density 2-8 storey building forms, with density focussed along public transport routes, on a grid with a ~200m interval and serviced by linear parks or a single large park. These general principles have been adopted in the proposed interventions, with some specific modifications to the different case studies – for instance, while 2-6 storeys Perimeter block development might be appropriate in central locations such as Subiaco, it is unlikely to be feasible in peri-urban case studies such as Southern River.
Table 4 Results of the design intervention workshop 1 A lower rating indicates that intervention should most reduce energy use and emissions.
Figure 3 The design intervention workshop.
1 Blank cells mean the spatial attribute was irrelevant to the group’s allocated case study.
Figure 4: An example of a group’s ratings of building types for likely emissions.
Figure 5: An example of a group’s design sketches – in this case for the Subiaco case study.
3.1.2 The literature on low-carbon neighbourhoods
To confirm the results of the design intervention workshop, we subsequently conducted a literature review to understand which design interventions would potentially reduce energy use and emissions.
The literature review related to prevailing theories such as Green Urbanism (Lehmann, 2010), New Urbanism (Congress of New Urbanism, 2016) and Climate Sensitive Urban Design (Lenzholzer, 2015) and relevant policy literature such as the WA Precinct Design Guide (Department of Planning Lands and Heritage, 2020).
Precinct configurations
There is a consensus in the New Urbanism and Green urbanism literature that higher building densities and a diversity of land uses should be within walking distance of transit stops, referred to as Transit Oriented Development (TOD). Indeed, many activities of daily living should occur within walking distance, allowing independence to those who do not drive, especially the elderly and the young (Congress of New Urbanism, 2016). The literature on TOD proposes that:
• Increasing the density of the neighbourhood population around transit nodes will support improved public transit services, make transit a viable alternative to automobiles, and reduce transport emissions (Congress of New Urbanism, 2016) The frequency of service and number of types of transit increase as the market of people willing and able to walk to the station increases. Concentrating development density in and around transit stops and adjacent to transit corridors maximizes this population (Farr, 2008).
• The denser a city, the less its residents drive, and the more they will walk and bike, a critical component to lessening oil dependence and reducing transport-related emissions (Newman, Beatley, & Boyer, 2009) which was found to be one of the largest precinct related emissions sources.
• Increased density and land use diversity contribute to the creation of more local jobs, which significantly lessens the impact of commuting. Indeed, TODs should contain a mix of activitiesdwelling, shopping, working, schooling, worshipping and recreating (Duany & Plater-Zyberk, 2015).
• Dense mixed-use urban development (e.g., including housing, retail or office space) can support district energy systems (central plants producing hot water, steam, and/or chilled water which flows through to dwellings), reducing carbon generation by 30% and energy consumption by as much as 50% (Farr, 2008).
Transit Oriented Development tends to take two forms:
• The first is urban density around a node (Department of Planning Lands and Heritage, 2020) Nodal density derives from ‘traditional neighbourhood development’ approaches, which proposes a model of urbanism that is limited in area and structured around a defined centre (Duany & Plater-Zyberk, 2015).
• The second is TOD along a corridor, which derives from Peter Calthorpe’s approach, which calls for developing Transit Boulevards, which are multi -functional arterials with transit designed to support mixed-use urban development (Calthorpe, 2002).
Emerging alternatives to TOD include Greenspace-Oriented Development (GOD). 2 While TOD correlates urban densification with mass transit hubs, GOD correlates urban densification with significant, upgraded parks within a 5-minute cycle or 15-minute walk of public transport in middlering suburbs The literature on GOD proposes that:
2 TOD and GOD can overlap to some degree (e.g., some TODs may contain major greenspaces).
• GOD can provide physical (van Dillen, de Vries, Groenewegen, & Spreeuwenberg, 2012) and mental (Astell-Burt & Feng, 2019) health benefits, increase the likelihood of walking thus reducing transport emissions (Giles-Corti et al., 2005), reduce urban heat island effects reducing operational emissions in adjacent buildings (Yu, Guo, Zeng, Koga, & Vejre, 2018) and ‘compensate’ residents living in medium-density settings for a relative lack of private greenspace (Chiesura, 2004).
• By being able to promote the socioeconomic rejuvenation of nearby urban areas (LaFarge, 2014), namely by increasing their property values (Crompton, 2005), GOD can foster urban redevelopment and densification (Mell, 2009).
Street layouts
There is a consensus in the New Urbanism and Green Urbanism literature that interconnected networks of streets should be designed to encourage walking, reduce the number and length of car trips, and conserve energy (Congress of New Urbanism, 2016). Related policy literature also suggests that street and block layouts should support an active transport network (Department of Planning Lands and Heritage, 2020).
While street grid spacing is not specified, a ‘fine network’ of interconnecting streets is recommended (Duany & Plater-Zyberk, 2015). Policy literature suggests that a block perimeter of around 600m provides a good balance of pedestrian and vehicular access and enables an efficient subdivision pattern (Department of Planning Lands and Heritage, 2020)
Climate Sensitive Urban Design (CSUD) theory proposes that streets should:
• Frame East-West running lots to enable east-west oriented rectangular-shaped buildings to minimize direct solar radiation (the bulk of solar radiation is intercepted by the east and west walls and roof of a building) (Oke, Mills, Christen, & Voogt, 2017).
• Enable buildings parallel or up to 30 degrees to the prevailing wind direction to maximise the penetration of prevailing wind through a district (Kusumastuty, Poerbo, & Koerniawan, 2018). CSUD theory also ventures that widening streets along the prevailing wind direction is highly effective in increasing ventilation (Kusumastuty et al., 2018). T
The policy literature also asserts that climate-responsive design approaches can reduce energy demand across the precinct (Department of Planning Lands and Heritage, 2020; Mazria, 1979; Morrissey, Moore, & Horne, 2011).
Climate Sensitive Urban Design proposes that street paving materials be reflective and permeable Permeable paving describes materials that are either porous (i.e., there are gaps in the aggregate material to allow water percolation) or blocks with interstitial spaces filled with porous materials that can support grass Because they can retain and lose water by evaporation, these surfaces also can moderate surface and air temperature (Oke et al., 2017). Street sections should also be generous enough to accommodate street trees. Street Trees can intercept most of the sun’s energy, reflecting some and absorbing some for photosynthesis, reducing the heat absorbed and released by the hard surfaces in streets, thereby cooling the cities during the day and overnight (Cooperative Research Centre for Water Sensitive Cities, 2020). The results of these interventions should be increased uptake of active transport modes and reduced cooling loads in adjacent buildings.
Built form
A consensus exists that sustainable urbanism is not achievable at low densities (Farr, 2008). As such, New Urbanism theory proposes that a broad range of housing types should be provided within neighbourhoods. The result is a range of price levels that can bring people of diverse ages, races, and incomes into daily interaction (Congress of New Urbanism, 2016). Building types can include garage apartments in conjunction with single-family houses, apartments above shops and apartment buildings adjacent to shopping and workplaces (Duany & Plater-Zyberk, 2015).
Green Urbanism and Climate Sensitive Urban Design theories affirm the importance of passive design (solar architecture) in producing low-energy, zero-emission designs and dramatically reducing reliance on mechanical cooling and subsequent building operation energy use (Lehmann, 2010).
The literature on solar passive design proposes that in hot climates:
• Rectangular-shaped building footprints should be oriented east-west to minimize direct solar radiation in summer (Oke et al., 2017). This situation is because the east and west walls intercept the bulk of solar radiation (aside from the roof of a building). This orientation also optimises solar access to buildings in winter (Department of Planning Lands and Heritage, 2020)
• Trees to the immediate north of the house should allow the sun into the house in winter and provide shade in summer. Therefore, they should be deciduous. Evergreen trees will shade the house's eastern and western sides (Hollo, 2008).
• A well-designed house should be elongated to open towards a private garden to the north that provides winter sun (Hollo, 2008).
• Window areas on the east and west building faces should be reduced, and window overhangs and hoods should be introduced to limit heat gain in a building and reduce mechanical cooling requirements (Bhoge, Nolan, & Pojani, 2020).
• Lightweight external cladding systems should be adopted to facilitate more effective building envelope insulation (B. Grace, 2007).
• Housing should have thermal mass in the form of concrete floor slabs to store the heat from the sun when required and provide a heat sink when the house needs to be cooled (Hollo, 2008).
• Buildings should have ‘cool roofs,’ which use reflective coatings to reduce roof surface temperatures and moderate heat transfer into the building (Oke et al., 2017).
• Lighter colours should be utilised on building faces exposed to direct sun to reduce the heat load on the building (Hollo, 2008).
• Buildings should allow ‘night purging’ where hot air can rise and be released by opening upstairs windows, drawing cooler air at lower levels (Hollo, 2008).
• Extended narrow house floor plans should be adopted (Landcorp, 2014) to optimise natural ventilation, particularly in the north-south direction (B. Grace, 2007), to reduce reliance on mechanical cooling (Department of Planning Lands and Heritage, 2020)
• Priority for northern orientation should be given to the living areas- living, dining, family, kitchens, and studies. Sleeping areas can be cooler and, therefore, face south. Utility rooms can be positioned to provide additional shade for the living spaces from the western or eastern sun (Hollo, 2008).
Green Urbanism theory suggests that built form should be constructed using regional materials and lightweight prefabricated systems, e.g., regional timber, to achieve shorter supply chains and reduce embodied emissions (Lehmann, 2010).
Open space structures
Green Urbanism theory proposes that urban areas should maximize landscapes, gardens and biodiversity (Lehmann, 2010). Green infrastructure provides many benefits to cities and urban residents - clean water, storm water collection and management, climate moderation, and cleansing of urban air, among others (Newman et al., 2009). One benefit of this emphasis on urban greenery is offsetting CO2 emissions (Newman et al., 2009). Numerous studies have also demonstrated the cooling effect of large-scale green structures on their surroundings. The name for these effects is very befitting: park cool islands (Lenzholzer, 2015). A direct temperature reduction due to the presence of a large urban park is about 1–2°C, preventing heat build-up and partitioning more heat into latent rather than sensible means (Rohinton, 2005). This can increase human comfort and, to some degree, reduce mechanical cooling loads in adjacent urban areas.
Water Sensitive Urban Design theory proposes that to maximise its cooling potential, open space systems should be designed to integrate rainwater collection, wastewater recycling and stormwater harvesting approaches to irrigation (Lehmann, 2010). Gravity can direct rainfall runoff from adjacent surfaces onto vegetation or into reservoirs, which helps sustain plants during dry weather by providing access to soil moisture stores (Cooperative Research Centre for Water Sensitive Cities, 2020).
The different theories tend to prioritise different open-space structures. New Urbanism tends to priorities smaller yet accessible neighbourhood parks (Bolleter, 2017), while Climate Sensitive Urban Design approaches favour the creation of larger parks, which can generate substantial park cool island effects (Lenzholzer, 2015). Finally, Water Sensitive Urban Design approaches prioritise linear parkland along drainage networks.
In conclusion to the two previous sections, a high degree of alignment exists between the findings from the interventions workshop and the academic and policy literature about the type of urban form that should deliver energy and emissions reductions. This form constitutes compact urban development (comprising a wide diversity of building types and land uses) arranged around transit (in a nodal or corridor form), structured by a fine interconnecting street grid. The built form should be responsive to climate, appropriately oriented and ventilated, and allow enough site area to sustain mature trees. While there was consensus on the importance of green infrastructure, there was less consensus on the appropriateness of different open-space structures, as these differed by theory.
3.1.3 The size and type of dwellings
Demographic analysis should also underpin planning for low-carbon neighbourhoods. Australia has the world's largest housing sizes per occupant (Figure 6), and new dwellings have become much larger over recent decades. The average size of new dwellings in Australia is 214m2 (Figure 7), while separate houses nearing 250m2 on average have come to dominate the Western Australia new dwellings market. At the same time, the average number of occupants in Australian households has been dropping steadily for many years. From 1990 to 2001, the number dropped from 2.8 to 2.6 people across Australia; the figures are similar for Perth, according to the 2021 ABS Census. The 2021 census reports some 560,000 empty bedrooms in Western Australia.
(Source: Australian Bureau of Statistics, Average Floor Area of New Residential Dwellings 12/04/2023)
The 2021 Census for Greater Perth reveals that most dwellings (over 70%) are separate houses, and 40% of those separate houses have only one or two occupants (Figure 8 and Figure 9).
Dwelling size is by far the largest leverage point concerning reducing greenhouse gas emissions in residential neighbourhoods, and there are many other potential benefits to reducing the size of dwellings. Not only do smaller dwellings (on average) lead directly to:
• Lower embodied emissions, lower operational emissions, more private open space (and more canopy);
• More dwellings per ha of developed land; lower land development costs per dwelling; lower pressure on greenfield sprawl; lower costs per dwelling (benefitting affordability); more dwelling completions per year (benefitting supply); and other density benefits such as improved public transport services
Irrespective of the form of housing, reducing the size of dwellings to match the actual demographics of the population better will assist in yielding these benefits.
The prevalence of separate (and large) houses on individual green title lots is a major contributor to the urban sprawl in Perth. As noted in the Phase 1 report, the energy associated with sub-division works significantly contributes to life cycle emissions per dwelling basis. Europe has a much more balanced mix of dwelling types (Appolloni & D’alessandro, 2021) (see Figure 10). While there is undoubtedly an underlying market preference for separate houses, considering realities such as
Figure 6 Dwelling size - various countries
Figure 7 New dwellings – WA
Figure 8 Perth housing mix by occupancy
Figure 9 Perth housing mix by dwelling type
current housing costs many people will happily consider more compact typologies (e.g. row housing) (Kelly, Weldmann, & Walsh, 2011, p. 2). Moreover, a larger proportion of alternative housing forms would substantially reduce the size of lots per person. Although it is often assumed that this means apartments, semi-detached and row housing, and townhouses also offer density benefits.
10 Dwelling mix in European countries
Table 5 and Figure 11 set out the size and type of dwellings that reflect Perth’s demographics and achieve higher density, and they are the basis for the case study interventions considered in the following section.
Table 5 Revised dwelling types and sizes
Figure
3.1.4 Interventions by case study
With these general principles from the design intervention workshop, literature review and demographic analysis in mind, the following section describes the existing case study precincts and the interventions applied in each case study area
Jindalee
The Jindalee case study is located near the coast in the northern Perth metropolitan area, some 40 km from the Central Business District (Figure 12).
Figure 11 Revised generic dwelling mix
Figure 12: Jindalee case study plan.
The Jindalee case study area is characterised by largely undifferentiated compact suburban fabric with large houses on medium size lots and minimal tree canopy coverage. The Jindalee case study suffers from several issues (Figure 14, Figure 15), compounding its energy use and related emissions These include:
• Subdivision works:
o High emissions from land clearing and site works (embodied emissions).
• Precinct configuration:
o Low densities in relation to transit fail to boost patronage (transport emissions).
• Streets:
o Narrow street sections inhibit tree planting (vegetation loss emissions).
o Lack of shade inhibits active transport modes (transport emissions)
o Car-dominated road environments discourage active transport (transport emissions).
• Built form:
o Large Gross Floor Area ( GFA) housing results in significant emissions associated with construction (embodied emissions)
o Poor building orientation increases heat gain and mechanical cooling (operational emission)
o Small backyards resulting from large GFA houses inhibit tree planting (vegetation loss emissions)
o Dark roofs promote mechanical cooling (operational emissions)
o Emissions-intensive masonry construction materials (embodied emissions)
• Open space system:
o The development model retains minimal remnant bushland (vegetation loss emissions).
o Small neighbourhood parks generate minimal cooling effects, thus compounding the use of mechanical cooling in surrounding housing (operational emissions).
Figure 13: The Jindalee case study precinct
The Jindalee study site 1 is characterised by largely undifferentiated compact suburban fabric with large houses on medium size lots and minimal tree canopy coverage.
The University of Western Australia uwa.edu.au Phase 2 report: An
Figure 14: Jindalee study site 1- existing.
While laneway-serviced small lots have been allocated along Reflection Boulevarde (pictured), there has been little increase in density or land use diversity per Transit Oriented development models.
Figure 15: Jindalee study site 2- existing.
In response to these issues, the proposed design interventions for the Jindalee case study (Figure 16) seek to lower the embodied, operational, transport and vegetation loss-related emissions. The resultant design is for a generally more compact, climate-responsive and well-forested suburban fabric, which increases significantly in density along the central spine of Reflection Boulevarde (per Transit Oriented development theory) The gross density of the revised case study site is around 35 dwellings per ha compared to 13 in the current configuration.
The predominant built form in Jindalee study site 1 comprises detached housing, row housing, and duplex housing, with a density of about R40 (Figure 17, Figure 18,). The urban form shown in study site 1 comprises about 70% of the total case study area.
The predominant built form in Jindalee study site 2 comprises detached housing, row housing, and 34 storey apartment buildings, with a density of about R100 (Figure 19, Figure 20) The urban form shown in study site 2 comprises about 30% of the total case study area.
Figure 16: The existing and proposed layouts for the Jindalee case study.
Figure 17 Jindalee study site 1 dwelling mix.
The vision is for a more compact, climate-responsive, well-forested suburban fabric. The predominant built form in the Jindalee study site 1 comprises detached housing, row housing and duplex housing.
Figure 18: Jindalee study site 1- proposed.
The vision is for a generally more compact, climate-responsive and well-forested suburban fabric, which increases density along Reflection Boulevarde's central spine. The predominant built form in the Jindalee study site 2 comprises detached housing, row housing and 3-4 storey apartment buildings.
Figure 19: Jindalee study site 2- proposed.
The specific interventions in both Jindalee study sites include:
• Subdivision works:
o Increased urban density reduces the area of required land clearing and site works (embodied emissions)
• Precinct configuration:
o Urban density increases adjacent to transit to encourage patronage (transport emissions).
• Streets:
o Pedestrianised road environments encourage active transport (transport emissions);
o Swales collect stormwater off roads and increase evapotranspiration cooling (operational emissions);
o Reinforced turf paving in shared zones provides evaporative cooling (operational emissions);
o Light emulsions on road surfaces reduce UHI (operational emissions) and
o N-S-oriented tree lines reduce the heat load on E- W house faces (operational emissions).
• Built form:
o A modest GFA results in emission reductions associated with construction (embodied emissions);
o Light-coloured roofs and walls reflect heat and reduce heat load (operational emissions);
o Living areas facing north reduces mechanical cooling/ heating requirements (operational emissions);
o Upstairs bedrooms purge heat at night (operational emissions);
o A diversity of housing (detached, duplex, row housing and apartments) provides efficient living options for small households (embodied emissions) and
o Lightweight construction materials result in emission reductions (embodied emissions)
• Open space system:
o N-S running linear open space system and accompanying tree lines reduce the heat load on E-W house faces (operational emissions).
Figure 20: Jindalee study site 2 dwelling mix
Southern River
The Southern River case study is located in the southeastern Perth metropolitan area, 25 km from the Central Business District ( Figure 21).
Figure 21: The Southern River case study plan.
The Southern River case study area is characterised by largely undifferentiated compact suburban fabric with large houses on medium size lots and minimal tree canopy coverage. The Southern River case study suffers from several issues (Figure 22), compounding its energy use and related emissions. These include:
• Subdivision works:
o High emissions from land clearing and site work, especially fill, to achieve separation between the water table and building forms (embodied emissions)
• Precinct configuration:
o Low densities in relation to transit fail to boost patronage (transport emissions)
• Streets:
o A narrow street section inhibits tree planting (vegetation loss emissions);
o Lack of shade inhibits walking (transport emissions) and
o Car-dominated road environments discourage active transport (transport emissions).
• Built form:
o Large GFA housing results in significant emissions (embodied emissions);
o Poor building orientation increases heat gain and mechanical cooling (operational emission);
o Small backyards resulting from large GFA houses inhibit tree planting (vegetation loss emissions);
o Dark roofs promote mechanical cooling (operational emissions), and
o Emissions-intensive masonry construction materials (operational emissions).
• Open space system:
o The development model retains minimal remnant bushland (vegetation loss emissions) and
o Small neighbourhood parks generate minimal cooling effects, thus compounding the use of mechanical cooling surrounding housing (operational emissions).
The site is characterised by largely undifferentiated suburban fabric with large houses on small size lots and minimal tree canopy coverage.
Figure 22: Southern River study site 1
In response to these issues, the proposed design interventions ( Figure 23) for the Southern River case study seek to lower the related embodied, operational, transport and vegetation loss-related emissions. The resultant design is for a generally more compact, climate-responsive and well-forested suburban fabric (R40), which requires less fill by draining towards Living Streams (or subsoil drains) at the back of lots (per Water Sensitive urban Design theory) There is also a small Apartment precinct (R100) with dwelling mixes, as set out in Figure 17 and Figure 20. The overall gross density of the case study area is around R23
The predominant built form in the Southern River study site 1 comprises detached and row housing (Figure 24).
Figure 23: The existing (left) and proposed(right) layouts for the Southern case study.
The vision is for a generally more compact, climate-responsive, well-forested suburban fabric that requires less fill by draining towards Living Streams (or subsoil drains) at the back of lots. The predominant built form in the Southern River study site 1 comprises detached and row housing.
Figure 24: Southern River study site 1- proposed.
The specific interventions include:
• Subdivision works:
o Increased urban density reduces the area of required land clearing and site works (embodied emissions);
o Site graded so that stormwater collects in Living Streams or subsoil drains behind dwellings to reduce fill requirements on private lots (embodied emissions).
• Streets:
o Pedestrianised road environments encourage active transport (transport emissions);
o Swale collects stormwater off roads and increases evapotranspiration cooling (operational emissions);
o Reinforced turf paving in shared zones provides evaporative cooling (operational emissions);
o Light emulsions on road surfaces reduce UHI (operational emissions) and
o N-S tree lines reduce the heat load on E-W house faces (operational emissions).
• Built form:
o Modest GFA results in emission reductions (embodied emissions);
o Light-coloured roofs reflect heat (operational emissions);
o Living areas facing north reduces mechanical cooling/ heating requirements (operational emissions);
o Upstairs bedrooms purge heat at night (operational emissions);
o A diversity of housing (detached, duplex, row housing and apartments) provides efficient living options for small households (embodied emissions) and
o Lightweight materials result in emission reductions (embodied emissions).
• Open space system:
o N-S running linear open space and drainage system and accompanying tree lines reduce the heat load on E-W house faces (operational emissions)
Ellenbrook
Ellenbrook, in the northeast of the metropolitan area, has been developing incrementally since 1991. It is twenty-two kilometres north-east of the Perth CBD and twenty kilometres from the district centre of Midland (Figure 25).
Figure 25: The Ellenbrook case study plan.
The Ellenbrook case study area is characterised by largely undifferentiated suburban fabric with large houses on medium to large size lots and minimal tree canopy coverage. The Ellenbrook case study suffers from several issues (Figure 26, Figure 27), compounding its energy use and related emissions. These include:
• Subdivision works:
o High emissions from land clearing and site works (embodied emissions).
• Precinct configuration:
o Low densities in relation to transit fail to boost patronage (transport emissions).
• Streets:
o A narrow street section inhibits tree planting (vegetation loss emissions);
o Lack of shade inhibits walking (transport emissions) and
o Car-dominated road environments discourage active transport (transport emissions)
• Built form:
o Large GFA housing results in significant emissions (embodied emissions);
o Poor building orientation increases heat gain and mechanical cooling (operational emission);
o Small backyards resulting from large GFA houses inhibit tree planting (vegetation loss emissions);
o Dark roofs promote mechanical cooling (operational emissions), and
o Emissions-intensive masonry construction materials (operational emissions)
• Open space system:
o The development model retains minimal remnant bushland (vegetation loss emissions) and
o Small neighbourhood parks generate minimal cooling effects, thus compounding the use of mechanical cooling surrounding housing (operational emissions).
The Ellenbrook study area 1 is characterised by largely undifferentiated suburban fabric with large houses on medium to large size lots and no urban density increase around park amenity.
Figure 26: Ellenbrook study site 1- existing.
Figure 27: Ellenbrook study site 2- existing.
In response to these issues, the proposed design interventions for the Ellenbrook case study seek to lower the related embodied, operational, transport and vegetation loss-related emissions. The resultant design (Figure 28) is for a generally more compact, climate-responsive and well-forested suburban fabric, which increases density around parks (per Greenspace- oriented development theory) The gross density of the case study site is around 25 dwellings per ha compared to the current value of 10.
The predominant built form in the Ellenbrook study site 1 comprises detached housing, row housing, duplex housing and 2-3 storey apartment buildings arranged around parks at R70 (Figure 29, Figure 30)
The predominant built form in the Ellenbrook study site 2 comprises detached housing, row housing and duplex housing at R40 (Figure 31).
Figure 28: the existing (left) and proposed (right) layouts for the Ellenbrook case study.
Figure 29: Ellenbrook study site 1 dwelling mix
The vision is for a generally more compact, climate-responsive, and well-forested suburban fabric that increases significantly in density around parks. The predominant built form comprises detached housing, row housing, duplex housing and 2-3 storey apartment buildings.
Figure 30: Ellenbrook study site 1- proposed.
The predominant built form in the Ellenbrook study site 2 comprises detached housing, row housing and duplex housing.
Figure 31: Ellenbrook study site 2- proposed.
The specific interventions include:
• Subdivision works:
o Increased urban density reduces the area of required land clearing and site works (embodied emissions)
• Precinct configuration:
o Urban density increases adjacent to significant parks and related cooling effects (operational emissions)
• Streets:
o Pedestrianised road environments encourage active transport (transport emissions);
o Swales collect stormwater off roads and increases evapotranspiration cooling (operational emissions);
o Reinforced turf paving in shared zones provides evaporative cooling (operational emissions);
o Light emulsions on road surfaces reduce UHI (operational emissions) and
o N-S tree lines reduce the heat load on E-W house faces (operational emissions)
• Built form:
o Modest GFA results in emission reductions (embodied emissions);
o Light-coloured roofs reflect heat (operational emissions);
o Living areas facing north reduces mechanical cooling/ heating requirements (operational emissions);
o Upstairs bedrooms vent heat at night (operational emissions);
o A diversity of housing (detached, duplex, row housing and apartments) provides efficient living options for small households (embodied emissions);
o Lightweight materials result in emission reductions (embodied emissions)
• Open space system:
o Urban density arranged around parks and related cooling effects to reduce reliance on mechanical (operational emissions).
Nollamara
The DPLH Working Group selected Nollamara as a typical example of ‘background infill,’ which occurs when suburbs are rezoned to facilitate subdivision (Figure 32, Figure 33).
The Nollamara case study is characterised by survey strata, generally single-storey infill dwellings referred to as ‘background infill’ and occasional unsubdivided blocks. On subdivided lots, tree canopy coverage is generally low, and large areas of the driveway are predominant. The
Figure 32: Nollamara case study plan.
Figure 33: Background infill in Nollamara
Nollamara case study suffers from several issues (Figure 34, Figure 35), compounding its energy use and related emissions. These include:
• Precinct configuration:
o Low-density, ad hoc background infill does not boost transit patronage (transport emissions)
• Streets:
o Lack of shade inhibits walking (transport emissions) and
o Car-dominated road environments discourage active transport (transport emissions).
• Built form:
o Large GFA housing results in significant emissions (embodied emissions);
o Poor building orientation increases heat gain and mechanical cooling (operational emissions);
o Small backyards resulting in high site coverage inhibit tree planting (vegetation loss emissions);
o Dark roofs promote mechanical cooling (operational emissions), and
o Emissions-intensive masonry construction materials (operational emissions).
• Open space system:
o Small neighbourhood parks generate minimal cooling effects, thus compounding the use of mechanical cooling surrounding housing (operational emissions)
The Nollamara case study is characterised by survey strata, generally single-storey infill dwellings referred to as ‘background infill’ and occasional unsubdivided blocks.
Figure 34: Nollamara study site 1- existing.
There is no negligible increase in urban density occurs along the central spine of the case study, Nollamara Avenue.
Figure 35: Nollamara study site 2- existing.
In response to these issues, the proposed design interventions for the Nollamara case study seek to lower the related embodied, operational, transport and vegetation loss-related emissions. The resultant design is for a generally more sensitive form of background infill that minimises site coverage and maintains urban forests while significantly increasing density along the central spine of Nollamara Avenue (per Transit Oriented Development theory). The gross density of the case study area is around 30 dwellings per ha compared to 22 in the exiting redeveloped case.
The predominant built form in the Nollamara study site 1 comprises existing detached housing and detached infill housing (Figure 37). Study site 1 comprises about 32% of the total case study area.
The predominant built form in the Nollamara study site 2 (along Nollamara Avenue) comprises existing detached housing and 2 -4 storey apartment buildings (Figure 36, Figure 38). Study site 2 comprises about 36% of the case study area.
About 32% of the case study area comprises unchanged lots
Figure 36 Nollamara study site 1 dwelling mix
The vision is for a generally more sensitive form of background infill, which minimises site coverage and maintains urban forests. The predominant built form in the Nollamara study site 1 comprises existing detached housing and detached infill housing.
Figure 37: Nollamara study site 1- proposed.
The vision is to significantly increase density along the central spine of Nollamara Avenue. The predominant built form along Nollamara Avenue comprises 2 -4 storey apartment buildings.
Figure 38: Nollamara study site 2- proposed.
The specific interventions include:
• Subdivision works:
o NA
• Precinct configuration:
o Urban density increases adjacent to transit to encourage patronage (transport emissions).
• Streets:
o Pedestrianised road environments encourage active transport (transport emissions) and
o Reinforced turf paving in shared zones provides evaporative cooling (operational emissions).
• Built form:
o Modest GFA results in emission reductions (embodied emissions);
o Light-coloured roofs reflect heat (operational emissions);
o The addition of only a single additional dwelling makes it easier to have living areas facing northeast to northwest, reducing mechanical cooling/ heating requirements (operational emissions);
o Upstairs bedrooms vent heat at night (operational emissions);
o A diversity of housing (detached, duplex, row housing and apartments) provides efficient living options for small households (embodied emissions);
o Lightweight materials result in emission reductions (embodied emissions), and
o Modest site coverage allows room for trees to reduce the heat load on E- W house faces (operational emissions)
• Open space system:
o NA
Subiaco
Subi Centro originally occupied over 80 hectares of former industrial land bounded by Salvado Road, Jersey Street, Roberts Road, Hay Street and Haydn Bunton Drive north of the Rokeby Road main street (Figure 39, Figure 40).
39: The Subiaco case study plan.
The redeveloped area of the Subiaco case study (‘Subi-Centro’) is characterised by 3- 5 storey perimeter block apartment buildings (including a supermarket and some department stores) adjacent to a train station with an underground train line. The Subiaco case study (Figure 41) exhibits several positive and negative characteristics that affect energy use and related emissions:
Figure
Figure 40: The Subi-Centro area
• Precinct configuration:
o Higher-density development adjacent to transit reduces car usage (transport emissions) and
o A mix of land uses adjacent to transit reduces car usage (transport emissions).
• Streets:
o Reasonable shade encourages walking (transport emissions) and
o Pedestrianised road environments encourage active transport (transport emissions)
• Built form:
o A wide diversity of housing stock suits different household types (embodied emissions);
o Sometimes, p oor building orientation increases heat gain and mechanical cooling (operational emission);
o High site coverage inhibits tree planting (vegetation loss emissions);
o Dark roofs promote mechanical cooling (operational emissions), and
o Emissions-intensive masonry construction materials (operational emissions)
• Open space system:
o NA
The site exhibits several positive and negative characteristics that affect energy use and related emissions.
Figure 41: Subiaco study site 1.
In response to these issues, the proposed design interventions for the Subiaco case study (Figure 42) seek to lower the related embodied, operational, transport and vegetation loss-related emissions. The resultant design is for a generally higher density urban form, which prioritises deep soil zones for tree planting and northern orientation for solar efficiency (per Green Urbanism and Climate Sensitive Urban Design theory).
The predominant built form in the Subiaco study comprises row housing and 3 -5 storey apartment buildings (Figure 43, Figure 44).
42: The existing (left) and proposed (right) layouts for the Subiaco case study.
The revised design for this case study site assumes that the densification (R160) occurs only on the portion of the site adjacent to the railway station (in green and to the north), which is around half of the total case study site.
Figure
Figure 43 The study site 1 dwelling mix
The vision is for a generally higher-density urban form, prioritising deep soil zones for tree planting and northern orientation for solar efficiency. The predominant built form in the Subiaco study site 1 comprises row housing and 3 -5 storey apartment buildings.
Figure 44: Subiaco study site 1- proposed
The specific interventions include:
• Precinct configuration:
o High urban density adjacent to transit to encourage patronage (transport emissions)
• Streets:
o Pedestrianised road environments encourage active transport (transport emissions) and
o Reinforced turf paving in shared zones provides evaporative cooling (operational emissions)
• Built form:
o Light-coloured roofs reflect heat (operational emissions);
o Living areas facing north reduces mechanical cooling/ heating requirements (operational emissions);
o Upstairs bedrooms vent heat at night (operational emissions);
o A diversity of housing (detached, duplex, row housing and apartments) provides efficient living options for small households (embodied emissions);
o Lightweight materials result in emission reductions (embodied emissions), and
o Modest site coverage allows room for trees to reduce the heat load on E- W house faces (operational emissions)
• Open space system:
o Deep soil zones in linear open spaces allow for substantial trees and related urban cooling (operational emissions).
3.2 Subdivision works
The section below discusses interventions to reduce carbon emissions that relate to case study subdivision works.
3.2.1 Clearing
Clearing of the sites, while detrimental to biodiversity, was not identified as a significant contributor to emissions in the Phase 1 report, representing only around 2% of lifecycle emissions per dwelling in the greenfield sites. In this research phase, it has been assumed that the same amount of clearing occurs per ha of development
3.2.2
Planting
Similarly, the sequestration of CO2 from landscaping planting had only a small influence on the Phase 1 results and has been assumed to be the same on a per-ha of development basis. The likely real mitigation benefit of the measures set out in Section 4.1.4 will be to reduce the urban heat island effect and potentially reduce summer air-conditioning loads. This benefit is complex to quantify and has not been considered in this phase of work,
3.2.3
Site establishment
The Phase 1 report identified that subdivision works on shallow groundwater locations such as Southern River and Ellenbrook significantly contributed to emissions (25% of lifecycle). This is attributed to the conventional approach to development in these sites, which comprise large quantities of fill, which are transported by heavy haul vehicles from offsite quarries and compacted using diesel-fuelled construction equipment.
Managing high seasonal groundwater has been a topic of debate since areas such as these began to be developed for residential purposes in the Perth metropolitan area. It was the subject of an expert panel report for the Cooperative Research Centre for Water Sensitive Cities in a report published in 2020 (Claydon, Thompson, Shanafield, & Manero, 2020). The report includes measures to reduce the amount of fill, including:
“Drainage designs that provide additional subsurface drainage from the rear of lots – for example, short and directly connected (to stormwater) subsoil drains could be installed in the expected location of the groundwater mound in the rear of each lot. Although this would create an element of drainage infrastructure that homeowners would need to manage (again, supported with appropriate education), responsibility for maintenance could be similar to that for on-lot sewerage. Demonstration sites to show the feasibility of this approach would also be beneficial.
Additionally, fill depths may be reduced if pipe grades can be made shallower, reducing the fall needed across the pipe length. This could reduce the need for fill.”
This study assumes that lots are separated by living streams or landscaped drains to avoid subsoil drains on private land. This is the arrangement depicted in Figure 24 (Southern River). Together with shallower pipe grades, this could reduce fill from 1-1.5m to 0.5m fill, subject to:
• Onsite management/treatment requirements for stormwater would need to be achieved using ‘above ground’ systems like rainwater tanks, rain gardens and within the ‘living stream’ itself (i.e. no soakwells).
• Turf species and other landscaping within the lots must be selected to cope with the shallow groundwater.
Based on further analysis of the Cerclos report used to determine subdivision emissions in Phase 1, it is estimated that emissions from the site formation component could be halved, leading to a reduction of overall emissions per ha by 36%.
For this research element, it has been assumed that this is an option for the case study sites at Southern River and Ellenbrook, while the Phase 1 calculations for the other sites have been retained. For the infill sites at Nollamara and SubiCentro, the Phase 1 report assumed negligible subdivision works. In this research phase, it has been assumed (somewhat arbitrarily 3) that subdivision works would lead to 20% of the emissions arising from the Jindalee site.
The research identifies that emissions associated with larger construction vehicles are likely to reduce only marginally over the coming decades (as discussed further in the Appendices).
3.3 Built form
The section below discusses interventions to reduce carbon emissions that relate to case study built form.
3 No information was available to identify subdivision related emissions in Phase 1. They would have likely been negligible for Nollamara where most work was undertaken within lots. Because, these emissions, and those for Subiaco were not represented in the Phase 1 work an arbitrary value has been assumed for this report.
3.3.1 Materials intensity
The Phase 1 report identified that most new housing construction involves concrete floor slabs, double brick external walls and either steel or tile roofing. Recent research by Curtin University (Hopkins et al., 2024) identifies that concrete is the most significant category in terms of annual material inflows for building stock in Greater Perth at 5.6 Mt (53.8%)
In this research phase, the emission intensity of alternative forms of construction was determined by analysing them using the eTool LCA software. A detailed description of the analysis is provided in the appendices.
Adopting lightweight envelope construction for housing, as described in Table 6, would significantly reduce embodied emissions (assuming existing emissions intensities), as illustrated in Figure 45.
The LCA assumes that all timber is “sustainable”, i.e., sourced from plantations that sequester carbon while growing, and that carbon is immobilised after that in built form. This assumption is discussed further later in the report.
4 Obtained from https://ahd.csiro.au/dashboards/construction/construction-overview/
Concrete and steel structural elements presently dominate the construction of apartments, while internal elements and finishes are similar to housing. The Phase 1 report adopted the eTool assumption that the embodied energy in conventional development is 576 kgCO2e/m2 GFA. Multistorey timber apartment buildings are a recent development in Australia, and in Western Australia, the Grange Development project in South Perth 5, claiming to be the world’s tallest timber building, was recently approved by the Metro Inner-South Joint Development Assessment Panel. This building of 200 apartments will combine lightweight, glued laminated timber and cross-laminated timber with lower amounts of steel and concrete than conventional construction methods.
For this study, we have relied on a detailed LCA of multi-storey timber residential buildings from the journal Energy & Buildings ((Lukić, Premrov, Passer, & Leskovar, 2021). This source reports that embodied emissions on a per m2 basis could be reduced by around 40% to 342 kgCO2e/m2. This value has been assumed for lightweight apartment construction.
3.3.2 Operational energy use
The Phase 1 report identified that actual operational electricity use in residential housing is much higher than would be predicted by reference to current code compliance. Analysis of additional data received from Western Power for the specific typologies studied in the Phase 1 report (which represented suburb-level data) was similar to or higher than previously reported. For this research phase, we have blended that data to produce an electricity demand based purely on a per m2 GFA basis. The demand calculation includes an assessment of the self-supply of electricity from private rooftop solar PV (see Sect 4.3.6 below). The previously obtained data from ATCO has been used to determine the demand for natural gas. The adopted assumptions for existing electricity and gas demand for electric-only and electric-plus-gas dwellings are illustrated in Figure 46 and Figure 47
EnergyConsult conducted an update of the Residential Baseline Study 6 (RBS) into energy use in the Australian and New Zealand Residential Sectors in 2020 for the Department of Industry, Science, Energy and Resources. This data includes an assessment of average residential electricity demand for Western Australia, which is summarised in Table 7.
As the average Perth house is 200-250 m2 this data is similar to the assumed demand in Figure 46.
The data reported in the Phase 1 report identifies that electricity use is around 50% higher in summer than winter which can be attributed to cooling loads. Application of the NCC thermal load equations for Perth suggests that cooling loads overall are around 20-30% higher than heating loads.
Natural gas demand has been assumed to be as identified in the Phase 1 report for houses retaining electricity and gas supplies (10-13 GJ/dwelling depending on dwelling size), consistent with the RBS report. The emissions intensity of natural gas has been assumed to decline by around 10% by 2050 on the basis that the network will combine that quantity of hydrogen by then
3.3.3 Energy efficiency
The energy demand for space heating / cooling housing is around 23% of the average total demand. Better design reflecting passive solar measures would improve energy efficiency due to the need for less active heating and cooling. However, assessing this potential benefit is beyond the scope of this research 7 , and improvements have not been explicitly considered in the modelling reported here. However, the RBS study includes overall energy efficiency projections, including appliances, lighting, and space conditioning, which have been adopted here. The RBS assumed reductions of 17% of appliance electricity consumption per dwelling between 2020 and 2040
3.3.4 Electrification
The Phase 1 report identifies from Western Power and ATCO data that, on average, around 80% of dwellings have a combined electricity and natural gas supply, although the figure is lower for apartments. The non-profit organisation Rewiring Australia has produced a report entitled Castles and Cars 8 , which sets out to transition to electricity-only housing in Australia. This projects a possible transition to 100% electrified homes by 2030. This report assumes a slower transition with 80% electrification by 2050.
7 This topic is covered by AUDRC’s other climate related research, the results of which will be available mid-2025.
8 https://www.rewiringaustralia.org/reports
3.3.5 Electrification of homes
3.3.6 Electricity self-supply
The Phase 1 report includes an analysis of the Western Power electricity data to evaluate the amount of electricity self-supplied by households via rooftop solar PV. This has been updated with the more recent Western Power data (Figure 48), which indicates that some 30-40% of electricity demand is currently being self-supplied.
In this phase of work, previously published research (W. Grace, 2023) has shown that self-supply is likely to grow significantly as the cost of solar PV and household batteries reduces. The projections from that modelling have been used here to project future self-supply in residential properties. Irrespective of the size of a solar PV array, the amount of electricity self-supplied is limited to around half of electricity demand. However, with battery storage, the amount of self-supply that offers a reasonable return to householders will likely grow, leading to 70% of dwellings having solar PV, with 50% also having batteries by 2059 (see Figure 49)
Figure 48 Household solar PV
3.3.7 Water and wastewater
The results of the Phase 1 study are assumed to apply to each type of dwelling Although the planning and design assumptions assume smaller dwellings, the amount of private open space per dwelling for housing typologies is somewhat larger. This would potentially lead to higher water demand for irrigation, but this has been neglected as emissions related to water and wastewater are relatively small
3.4 Transport
The section below discusses interventions to reduce carbon emissions that relate to case study transportation.
3.4.1 Travel patterns
The Phase 1 report concluded that emissions from private vehicles ranged from 30 – 45% of total lifecycle emissions based on modelling from the DoT’s STEM simulations. The planning interventions contemplated in this phase of research could potentially influence private transport emissions in several ways:
• distribution of density better aligned with public transport routes, making access easier and, therefore, more attractive;
• reduced on-lot parking (maximum of 1 bay per dwelling);
• improved walkability (e.g. shade and improved pedestrian access to local amenities, including public transport nodes);
• enhanced micro-mobility (e.g. improved cycleways, e-bikes/scooters, electric skateboards); and
• improved local public transport (e.g. local destination-related bus transit).
However, it has been determined that the densification of the case study sites and the factors outlined above cannot be realistically modelled with STEM regarding trips “produced” or “attracted” to/from key destinations or local travel. Accordingly, the vehicle-kilometres-travelled (VKTs) have been assumed to be unchanged in this phase of work. The VKTs were roughly related to distance from the CBD (see Figure 50)
Figure 49 Solar PV and battery take-up
3.4.2 Vehicles
In this phase of the research, two factors have been considered:
• Fuel efficiency improvements in internal combustion engine vehicles (ICEV); and
• The take-up of electric vehicles.
The former has been taken from a report by the Global Fuel Economy Initiative (GFEI) (Kodjak & Meszler, 2019), which projects that emissions per km for passenger cars could improve from the present average value of 210 gCO2e/km to 120 gCO2e/km by 2050 9
CSIRO has produced projections for all types of electric vehicles (CSIRO, 2023a) under three scenarios “Progressive Change,” Step Change,” and “Green Energy Export”. The CSIRO data is provided as a projection of fleet share from 2025 to 2055. A more conservative trajectory has been adopted for this study, as shown in Figure 51. The Australian Electric Vehicle Industry Recap report of 2023 states that “EVs now represent approximately 1% of the total light vehicle fleet in Australia (31 Mar 2024) ”
9 ICE vehicles include hybrid vehicles that maintain their charge solely through ICE-derived energy, but exclude plug-in hybrid and electric vehicles.
Figure 50 Private VKTs per dwelling
3.5 Electricity in the SWIS
Decarbonisation of the SWIS is a major element of the Western Australia government’s Sectoral Emissions Reduction Strategy (SERS) 10. The report states:
“By 2050, 96 per cent of energy consumed is projected to come from renewable generation, compared with 34 per cent currently in the SWIS and 2 per cent in the Pilbara.”
The trajectory adopted for this study is shown in Figure 52.
The interventions described in Section 4 have been incorporated into a system dynamics model using the Vensim software 11 . Systems dynamics models simulate changes to stocks over time (e.g. take-up of private solar) by combining interdependence between variables with feedback (e.g. the penetration of EVs) to enable an understanding of how a change in one or more variables affects others. The structure of the model facilitates exploration of many combinations of intervention and comparisons with the Phase 1 results, referred to as the “Baseline”.
4.1.1
Model structure
The model is constructed in modules that calculate emissions on a per-dwelling basis for several urban typologies, namely:
Table 8 Precinct typologies
Precinct typology Applicable case study sites
Greenfield housing precinct Jindalee, Southern River, Ellenbrook
Greenfield apartment precinct Jindalee, Southern River
Greenfield – GOD precinct Ellenbrook
Infill – retained housing precinct Nollamara
Infill – new housing precinct Nollamara
Infill – TOD precinct SubiCentro
Each of these precinct typologies contains the dwelling mix per ha (of lots), i.e. the type and size (i.e. floor area) of each dwelling type, together with the lot area for each type.
The dwelling types considered are:
• Separate houses;
• Semi-detached houses;
• Rowhouses;
• Townhouses;
• Apartments in 3-storey buildings;
• Apartments in 4-storey buildings; and
• Apartments in 5-storey buildings.
4.1.2
Subdivision emissions
Subdivision emissions are based on four ground conditions, namely:
• Shallow groundwater sites – conventional fill;
• Shallow groundwater sites – reduced fill;
• Sandy soil sites; and
11 https://vensim.com/
• Infill sites
4.1.3 Vegetation – clearing and planting
The results of the Phase 1 study are retained but lead to lower values per dwelling basis due to the assumed density increases.
4.1.4
Embodied energy of built form
The embodied emissions of each dwelling type are determined by its construction materials (see Sect 4.3.1), namely:
• Conventional; and
• Lightweight
4.1.5 Operational energy emissions
Operational energy use for dwellings is calculated separately based on dwelling size, which varies over time based on projections for:
• The fraction of electric-only and electric + gas houses;
• Electrical efficiency of household appliances;
• The take-up of solar PV and/or batteries and
• The take-up of EVs
Emissions intensities for electricity and natural gas are also assumed to vary over time, and these are applied to the energy calculations to provide annual emissions per dwelling
4.1.6 Private vehicle emissions
Emissions from private vehicles are based on:
• The fraction of EVs varies over time and impacts electricity demand in homes and
• The fraction of ICEVs and their emissions intensity varies over time.
4.1.7
Emissions from Water and Wastewater
The results of the Phase 1 study are retained and calculated for each dwelling type. The Water Corporation’s emissions intensity is assumed to decline in line with the SWIS.
4.1.8 Exclusions
Several emissions sources are not included in the model, including:
• embodied emissions in vehicles, household furniture, fittings and appliances;
• operational emissions associated with public transport and other electric mobility devices, and
• any changes to transport emissions that may arise from ride-sharing (via autonomous vehicles or otherwise)
4.2 Controls
The model is configured to report embodied, operational and 50-year lifecycle emissions for each precinct type, which are compiled to report emissions for each case study site. For this report, results have been produced that reflect emissions associated with each level of control as set out in Figure 1, i.e.:
• Planning & design;
• Resident choices;
• Other government policies and the market
4.2.1 Scenarios
To avoid too many combinations of intervention, there are some common assumptions underlying all scenarios:
• Transport
o Continuing improvement in the fuel efficiency of ICEVs
• Planning & design
o Adoption of revised urban form (types and sizes of dwellings)
• Consumer choices
o Continuing energy efficiency measures and
o Business as usual private travel patterns.
The model has been used to test the main uncertainties with major impact:
• Resident choice
o Electrification of homes and private vehicles;
o Projected take-up of solar and batteries and
o House construction materials
• Other government policies and the market
o SWIS decarbonisation
5. Results of modelling
The following section shows the 50-year lifecycle emissions for each case study site compared to the results of the Phase 1 study (noted as the Baseline 12). Annual emissions summaries that illustrate changes in operational emissions over time are included in the Appendices. For each precinct, the scenarios are compiled cumulatively as follows:
Table 9 Intervention scenarios
Tag Scenario
P&D
+ Home elect
+ Materials
+ SWIS
P&D+SWIS only
5.1 Greenfield
5.1.1 Jindalee
• Planning and design measures only
• Planning and design measures/ plus
• Home electrification, solar and battery takeup, EV takeup
• Planning and design measures, plus
• Home electrification, solar and battery takeup, EV takeup, plus
• Home construction with lightweight materials
• Planning and design measures, plus
• Home electrification, solar and battery takeup, EV takeup, plus
• Home construction with lightweight materials, plus
12 There are some minor changes to the Baseline values compared to those reported in the Phase 1 report, including the addition of nominal subdivision related emissions.
5.1.2 Southern River
Table 11 50-year lifecycle emissions (kgCO2e/dwelling) - Southern River
Figure 53 50-year lifecycle emissions - Jindalee
Figure 54 Impact of interventions - Jindalee
Figure 55 50 year lifecycle emissions (kgCO2e/dwelling) - Sthn River
Figure 61 50 year lifecycle emissions (kgCO2e/dwelling) - SubiCentro
Figure 62 Impact of interventions - SubiCentro
Note that the Baseline data for SubiCentro from the Phase 1 research incorporates the entire case study site, whereas this phase only includes the TOD area around the station (see Figure 42)
5.3 Summary
The cumulative emissions of all the case study sites are depicted in Figure 63
Figure 63 Summary of modelling results
In 2019, the State Government set an economy-wide target of net zero emissions by 2050 and committed to working with all sectors of the economy to achieve this goal. The State Government also set a target for reducing emissions from State Government operations of 80 per cent below 2020 levels by 2030. The Climate Change Bill 13 will enshrine the state’s long-term target of net zero emissions by 2050, provide statutory requirements to develop policies to reduce emissions, set interim emission reduction targets, and enhance climate resilience.
The operational emissions in this study derive from the following (in order of diminishing magnitude):
• Household energy supply (electricity plus gas);
• Vehicle emissions from ICEVs;
• Water and wastewater; and
• Plantings.
The impact of the interventions on annual operational emissions is depicted in Figure 64
Figure 64 Annual emissions
13 At the time of writing the Bill has been introduced into Parliament but not enacted.
Note that the annual improvements in P&D emissions result from the measures that are locked into all scenarios, i.e. improvements in energy efficiency of household appliances and ICEV fuel efficiency (see Section 5.2.1). The improvements in the other scenarios result from the incremental changes, e.g. the take-up of home batteries and EVs, and decarbonisation of the SWIS.
6. Discussion and conclusions
The purpose of this research phase is to evaluate the potential reductions in emissions from a range of interventions
6.1 Greenfield sites
6.1.1
Planning and design measures
The focus of these interventions for greenfield development sites revolves around the reconfiguration of dwelling types and sizes to better reflect the existing and likely future demographics of the population in the Perth metropolitan area. The result of right size (and less expensive) housing would be significantly higher gross dwelling densities, delivering more private open space to facilitate trees and gardens and optimising solar access for rooftop solar PV and winter passive heating. From a developer perspective, this would lead to a larger number and greater diversity of lots per ha of development. From a builder’s perspective, this would lead to more dwelling completions per m2 of constructed built form.
Compared to existing forms of development, on a per-dwelling basis, these measures result in:
• lower levels of embodied carbon in both the subdivision works and the built form, and
• lower operational energy demand
The measures are particularly effective for the greenfield sites due essentially to the larger increase in gross dwellings per ha.
6.1.2
Subdivision emissions
The model assumes the same subdivision works emissions per ha of development land under the planning and design measures. This leads to a 50-60% reduction in lifecycle subdivision-related emissions per dwelling. For the Southern River and Ellenbrook case study sites, the opportunity to reduce fill reduces those values by a further 15%.
Relatively high emissions associated with subdivision works are influenced by the likely slow decarbonisation of construction vehicles.
6.1.3
Home electrification
The selected interventions include:
• increasing penetration of rooftop solar PV, together with home batteries, driven by the financial incentives of homeowners to reduce electricity costs;
• a gradual electrification of homes and
• the take-up of electric vehicles
These measures alone have the potential of reducing lifecycle per dwelling energy supply and transport emissions by around 40%, despite the adoption of EVs increasing the demand and emissions from energy supply (see Figure 65).
These interventions cannot be controlled through any regulation presently contemplated, although the National Construction Code 2024 introduces stricter energy efficiency requirements and a whole-of-home energy use allowance, which incentivise the integration of rooftop solar and batteries. It is also possible that future versions of the NCC could require onsite solar.
6.1.4 Embodied emissions
The embodied emissions in this research phase have been assumed to be the same as in Phase 1 of the research on a per m2 GFA basis. The reduced average size of dwellings alone leads to 30-40% reductions in the built-form lifecycle embodied emissions per average dwelling, noting that the figures are dominated by the building envelope, conventionally comprising concrete, steel and brick. Substituting these materials with a lightweight form of construction (see Sect 4.3.1) leads to major reductions in embodied emissions of around 50% per m2 GFA. This reduction is mainly influenced by the LCA assumption that timber is sustainably sourced, producing negative emissions, which is challengeable. This is discussed further in the Appendices.
Although this report assumes that residents choose construction materials, it is possible that regulations could follow. Indeed, reporting of embodied carbon is to be introduced in the 2025 Australian National Construction Code (NCC) It is possible that a minimum standard could be adopted in NCC 2028.
6.2 Infill sites
The reduction in emissions per dwelling is lower in the infill sites of Nollamara and Subiaco, as densities are already much higher than the greenfield sites. However, the reductions are still significant at around 30% per dwelling due to planning and design measures alone.
The revised urban layout of Nollamara illustrates that densities could be higher than business as usual through the measures assumed here:
• retention of around 30% of existing lots and houses;
• much more modest subdivision of a further 30% of lots with a single additional dwelling and
• a dense transport-oriented corridor development (see Figure 35).
Figure 65 Lifecycle emissions per dwelling for home electrification (Southern River example)
There are challenges with the achievement of the lot amalgamation necessary to deliver such corridor development. This issue, together with planning targets for greenfield and infill, will be canvassed in the final report.
7. Next steps
The first phase of research involved the identification of the primary contributors to greenhouse gas emissions in neighbourhoods through an analysis of selected case study sites This current phase of the research aims to develop a working model of urban emissions as a basis for developing recommendations for planning policy.
The final report will contain a summary of the entire research project and make recommendations related to the key objectives of the project, i.e.:
• How emissions can be reduced through urban planning and design interventions (guided by policy);
• how the modelling and reporting of emissions would occur at the district and local structure plan stages and how these could be followed through to implementation; and
• identify key indicators and assessment methodology applicable at the district and local structure planning stages for residential areas.
The final report will also reflect on the planning system, including the hierarchy of documents that seek to guide development (e.g., State Planning Policies, Design Codes and the Metropolitan region Scheme) in respect of their potential role in enabling the design interventions essential for the delivery of low-carbon neighbourhoods.
The cost-benefit of the measures identified in this report is beyond the scope of this research but will however be discussed in the final report.
8. References
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Appendix A
Emissions Trajectories
Scope
Emissions trajectory pathways across each of the selected areas:
1. Transport, Vehicles & Equipment
1.1. Electric Vehicle (EV) Adoption
1.2. Vehicle Emissions Intensities (Internal Combustion and EV)
1.3. Construction Vehicles and Equipment
2. Household Energy
2.1. Natural Gas and Electrification
2.2. Appliance Energy Efficiency
3. Construction Materials
3.1. Steel
3.2. Cement/Concrete
3.3. Brick
3.4. Wood
4. Other
4.1. Trends in LCA
4.2. SWIS Renewable Generation
Data Selection
Data Source Priority
The literature review highlights a range of data sources that could be used to develop emissions trajectories across sectors or specific areas. For this study, trajectory data sources have been categorised into the following two groups:
1. Projections
Emissions trajectories are developed by sector advisory bodies, research groups, consulting firms, and/or government policy, primarily to review one or more circumstantial scenarios. They typically:
a. reflect on current and/or future scenario(s)
b. highlight the level of impact of specific interventions
c. or review the overall trajectory of the current or intended specific new policy
Projections may refer to emissions targets (net-zero by 2050 or Paris Agreement 1.5oC pathways, for example) as a reference measure but are not explicitly derived to deliver a target.
2. Strategies
Emissions trajectories are developed by industry groups or businesses within a sector to define a pathway to meet a specific emissions objective.
Projections are considered more robust and are th is study's preferred sources for emissions trajectories. Many Net-zero strategies are still dependent on the following:
i. Businesses are fully unpacking their Scope 3 emissions and understanding the impacts of tackling them.
ii. Integration of future technologies that are not yet well-proven.
A distinction between the two source categories is not always possible.
Where possible, data based on WA trajectories is preferred.
Limitations
Many of the data sources and studies referenced in this report have their own assumptions or projections for relevant trends, typically national or state-specific. As such, they may differ from the state or suburb-level trends used to develop this study's model for Phase 2. This potentially reduces the accuracy of the selected trajectories and while the base trends have been reviewed, it was not practical to recalculate each dataset to align the base trends to this study.
This typically includes base trends for population growth, home ownership and dwelling types, amongst others
Transport, Vehicles and Equipment Pathways
Electric Vehicle (EV) Fleet Share
Objective & Approach
Define the projected EV fleet share (%).
The fleet share is used with projected VKTs and emissions intensities (10.1.5) to calculate a pathway for overall emissions for passenger vehicles and light commercials.
Applies To Passenger Vehicles (PV), Light Commercial Vehicles (LCV)
Primary Source
Type
Limitations
Assumptions
CSIRO - (CSIRO, 2023a)
Projection
Vehicle types
• ICE will retain 1% fleet share for specialist uses
• PHEV will reduce to zero as BEV and FCEV range increases
• 10-20-year delay between sales share and fleet share
CSIRO has developed a set of projections for all types of electric vehicles (CSIRO, 2023a) under three scenarios “Progressive Change,” Step Change,” and “Green Energy Export” as per those defined by AEMO.
The projections cover all categories of vehicle (PV, LCV, HV) and all-electric vehicle types:
1. Battery Electric Vehicles (BEV)
2. Plug-in Hybrid Electric Vehicles (PHEV)
3. Fuel Cell Electric Vehicles (FCEV)
CSIRO data is provided in a projection of fleet share from 2025-2055, so no further calculation was required.
Corroboration
CSIRO projections and scenarios are considered well-developed, but further data was sought to verify if this projection aligns with other sources, particularly for WA. A sectorial emissions strategy from WA’s DWER (DWER, 2023) was reviewed and found to be in general alignment with CSIRO’s Green Energy Export scenario, although the predicted rate of the DWER projection is more frontloaded.
Vehicle Emissions Intensities (Internal Combustion and EV)
Objective & Approach
Define the projected ICE and EV emissions intensity (% change)
The emissions intensities are used with projected VKTs and fleet share to calculate a pathway for overall emissions for passenger vehicles and light commercials.
Applies To Passenger Vehicles (PV), Light Commercial Vehicles (LCV)
Primary Source New Vehicle Efficiency Standard (NVES) – DITRDCA (DITRDCA, 2024)
Type
Limitations
Assumptions
Projection – Legislation
• Applies to ICE and LZEV – contribution of LZEV approximately corrected according to CSIRO EV Fleet Share %.
• Emissions caps are only detailed out to 2030.
• Headline limits for applicable vehicles remain as per the March 2024 revision.
• Vehicle categories remain at broadly current ratios between PV / LCV.
The NVES has now been legislated under the New Vehicle Efficiency Standard Act 2024, which will commence in January 2025 (DITRDCA, 2024). The standard will apply to new cars sold in the Australian market and sets a regulatory obligation for manufacturers to provide vehicles with a salesweighted average below the vehicle emissions cap. The cap is reduced over time and provides a credit/penalty measure for those who exceed or fail to meet the cap.
Internal Combustion Emissions Intensity
NVES emissions intensity caps will apply to a manufacturer’s range of vehicles and will include lowto-zero emissions vehicles (LZEV), so this trajectory relates to both:
1. Improvement in ICE vehicle emissions intensity
2. Increasing ratio in ZEVs
It is impossible to disaggregate the impact of these factors, nor is there another source for ICE-only emissions intensities reflecting the NVES.
Electric Vehicle Emissions Intensity
Due to the inclusion of PHEVs in CSIRO’s EV category, some fossil fuel combustion emissions are expected from this category.
The ratio of PHEV to total EV was 12.1% for WA in 2023 (Department of Transport, 2023), with an emissions intensity based on 2022 data (National Transport Commission, 2023) of 43 gCO2/km, providing a total average emissions intensity for the broader EV category of 5.2 gCO2/km. CSIRO expects a drop to zero by 2050, so a linear reduction was assumed from the 2023 data.
Corroboration
The NVES is a recent development; no additional trajectories that reflect this standard could be identified. Previous studies of vehicle emission intensity projections (DISER, 2022) do not reflect the potential impact of the NVES.
Vehicle Kilometres Travelled (VKTs)
As mentioned above, VKTs for passenger vehicles and light commercials were provided by DoT and are used in tandem with emissions intensities and fleet share data
The Global Fuel Economy Initiative (GFEI) 14
The GFEI was founded in 2009 to promote and support government action to improve the energy efficiency of the global light-duty passenger vehicle fleet. For this study, we have relied on the GFEI Working Paper 20, “Prospects for fuel efficiency, electrification and fleet decarbonisation” for passenger vehicles.
This report projects that emissions per km for passenger cars could improve from the present to 120 gCO2e/km by 2050.
Construction Vehicles and Equipment
Objective & Approach
Define the projected fleet share (%) of low-emissions construction equipment and related vehicles.
Unlike typical transport vehicles, VKT’s are unavailable, so this fleet share trajectory is used directly with residential construction emissions from the Cerclos LCA study.
Applies To
Three defined categories:
1. Small Construction Equipment
2. Large Construction Equipment
3. Heavy Vehicle (exclusive use for road transport of construction equipment)
14 https://www.globalfueleconomy.org/
Primary Source Lendlease / UQ (Smith et al., 2022)
McKinsey (McKinsey, 2021)
Type Strategy / Projection
Limitations
Assumptions
• Low-resolution trajectory to 2030.
• Relies on renewable diesel to decarbonise large equipment.
• Renewable diesel provides a 65% reduction in emissions intensity (California Air Resources Board, 2024)
The impact of decarbonisation pathways for these construction equipment and vehicle types depends on their respective contributions to construction emissions during a site’s life cycle. These emissions can vary depending on the development type and reliance on different equipment. The following process is detailed in the sections below:
1. Identify the category respective emissions contributions from applicable residential development LCA data.
2. Develop pathways for each category.
3. Apply the category pathways to the identified emissions contributions.
While the Lendlease/UQ reports propose a top-level electrification trajectory for all construction machinery, this report uses category-specific projections to understand better the potential impacts on the selected development sites and typology.
Equipment Emissions Proportions for Residential Developments
Residential LCA data was provided by Cerclos (Cerclos, 2023) for three Perth, WA developments, as used in Phase 1 of this study. Detailed data was provided, which allowed the identification of all relevant equipment types, typically including compactor rollers, concrete pumps, excavators, backhoes, etc. Emissions were totalled across the life of the dwellings. Although briefly discussed, emissions patterns across the life cycle, or specific reasons for variations between sites, are not analysed in detail in this section.
Comparative data for the three developments is presented in Table 15 and visualised in Figure and highlights the significantly different scale of emissions impacts, but the proportional contributions across equipment categories fall within a narrower range of 61.1% – 81.2%.
Table 15 – Equipment Emissions from Dwelling Life Cycle, by Site
Figure 1 - Equipment Emissions from Dwelling Life Cycle, by Site
Movement of trade staff to and from the site is yet to be confirmed but may range from 2-8% of total emissions categorised under construction.
Small Equipment Emissions Intensity
Small equipment typically includes concrete pumps, skid steers, elevated platforms and miniloaders. Small equipment's size and power requirement suggest it can be readily electrified due to relatively similar size and capacity requirements from growing EV and battery technologies.
Data is not directly provided but is visually indicative (Lendlease, 2022) that most small equipment will have electrification options by 2025 and around 50% of the “small excavator” sub-category. Therefore, an approximate value of 70% of the electrification potential is given to this category for the 2025 reduction potential. This is projected to increase to 100% by 2030.
Emissions intensity is taken as a percentage reduction from 100% of current values to the effective reduction due to the fleet share across the time horizon.
Electrified proportions of the equipment are assumed to have an emission intensity of zero, and additional electricity consumption is captured and allocated elsewhere.
Large Equipment Emissions Intensity
Large equipment typically includes bulldozers, graders, compactor rollers, loaders, etc. This large machinery's size and power requirement suggest it will take longer to electrify and that the 2025-2030 timeline relies on a renewable diesel alternative.
Bushmead Orion Hamilton Hill All / Average
There remains some uncertainty on the availability of renewable diesel and whether manufacturers will develop these options instead of solely focusing on more long-term electrification technologies. However, given that the renewable diesel scenario presents a more conservative emissions reduction, it can still be considered representative of a step change to electrification in terms of the gradual reduction in electrification. This may be allocated to either renewable diesel options or gradual electrification.
Leandlease suggests that approximately 30% of large equipment (particularly large excavators and earthworks sub-categories) can transition to renewable diesel by 2025. Virtually 100% of large equipment can move to renewable diesel by 2030.
Emissions intensity is reduced from 100% of current values to 65% of the effective reduction due to the fleet share across the time horizon.
Heavy Vehicles (road) Emissions Intensity
Heavy vehicles considered under the “construction” category for this study include:
1. Bulk Material Transport – medium and heavy rigid vehicles
2. Equipment Transport – medium rigids with trailers, some articulated vehicles
Global fleet share projections are provided by McKinsey (McKinsey, 2021), as Australian and West Australian projections are still under development. Data is presented by sales share % out to 2050 and is approximately translated into fleet share by applying a 15-year delay.
Emissions intensity is taken as a percentage reduction from 100% of current values to the effective reduction due to the fleet share across the time horizon. As per other sections, increasing electricity grid consumption is accounted for elsewhere.
Notes
Cranes are included in “large equipment” for this report, but it is noted that their stationary nature may provide more rapid electrification than other types in this category. However, a brief review indicated few electric crane options currently on the market in Australia, and as this individual pathway cannot be reasonably defined, cranes remain in the “large equipment” category.
Renewable diesel is defined as a biofuel from entirely renewable sources and presents an approximately 65% reduction in emissions intensity (California Air Resources Board, 2024). B5 and B20 biodiesel could also play a role in the transition to renewable diesel, but they are considered interim, and a trajectory has not been included in this study.
Concrete pumps are assumed to be trailer-mounted equipment and are included in the “small equipment” category. Larger, vehicle-mounted pumps would present a different electrification trajectory, but these are primarily used in multi-storey developments and are assumed to be excluded from this report. (review)
Corroboration
For construction equipment, there appear to be few Australian studies that can be used to identify the trajectories discussed above. Similar projections in Australia cannot quickly corroborate the
Lendlease/UQ reports, and typical other reference points in Europe or America are not considered representative of the Australian market.
For this study, it has been assumed that net emissions from construction vehicles involved in subdivision works will be halved by 2075 through electrification and fuel efficiency.
Household Energy Pathways
Natural Gas Transition
Objective & Approach
Define the projected consumption of NG, LPG and Electricity per dwelling.
Projected consumption can be combined with current or projected emissions intensities from the respective fuels/sources to define overall emissions.
Applies To NG, LPG, Electricity
Primary Source Energy Consult’s Residential Baseline Study “RBS2.0” (Energy Consult, 2020)
Type Projection
Limitations
• Comprehensive study, but data accuracy across 20 years at this resolution is potentially limited.
Energy Consult has expanded the Residential Baseline Study into the updated RBS2.0, which provides a detailed dataset for residential energy usage across Australia and WA.
Occupied Dwellings
RBS2.0 provides data for fuel use and end-use (appliances) by state, but per-dwelling fuel consumption data is only provided in aggregate form for all of Australia. However, total fuel consumption by state is provided but must be divided by dwelling quantity to identify the correct per-dwelling usage.
Per-dwelling usage is critical to estimate as it represents changes in fuel consumption from the expected improvement in appliance efficiencies.
Dwelling projections are included in RBS2.0 but include both occupied and unoccupied, and therefore, a calculation of typical ratio must be applied to define per-occupied-dwelling consumption correctly.
2020 data was used to identify a typical 87.3% ratio of occupied dwellings. Some uncertainty remains regarding how this data was originally calculated, but uncertainty in the scale of fuel use does not affect the reliability of the trend trajectory.
Occupied WA dwellings are projected to grow from 965,052 to 1,305,651 between 2020 to 2040.
Fuel and Electricity Consumption
In 2020, approximate consumption was 10.9 GJ, 1.2 GJ and 5736 kWh for NG, LPG and electricity per occupied dwelling, respectively.
RBS2.0 suggests a trajectory to 2040 for approximate consumption of 8.9 GJ, 1.3 GJ and 4742 kWh for NG, LPG and electricity per occupied dwelling, respectively.
Corroboration
RBS2.0 trajectory for fuel consumption broadly aligns with CSIRO’s CRD Pathway (CSIRO, 2023b), which provides a trajectory for emissions reductions from fuel switching, although no further data is available on the specific fuels in this trajectory.
Other sources for NG forecasts are available from WA’s Emissions Reduction Strategy (DWER, 2023) and AEMO’s Future Gas Report (DISR, 2024). These sources are similar in their proposed trajectory for NG consumption but apply to all sectors, so residential proportions cannot be extracted.
Hydrogen NG Blend
Hydrogen blending into the NG mix is an alternative approach to reducing NG emissions intensity, and while the reality of achieving this depends on many factors, it can be used to reflect an alternative pathway.
WA’s Renewable Hydrogen Strategy and Roadmap (DJTSI, 2024) projects a 13% reduction in emissions intensity from a 10% hydrogen blend in NG by 2030. A brief review suggests that beyond 10%, the potential hydrogen blend is uncertain.
Appliance Energy Efficiency
Objective & Approach
Applies To
Primary Source
Type
Limitations
Define the projected consumption of electricity use from appliance energy efficiency.
Projected consumption can be combined with current or projected SWIS emissions intensity.
Electricity and household appliances
Energy Consult’s Residential Baseline Study “RBS2.0” (Energy Consult, 2020)
Projection
• Comprehensive study, but data accuracy across 20 years at this resolution is potentially limited.
The impacts of appliance energy efficiency improvements are captured in the electricity consumption trajectory in Section 0. However, isolating this trajectory for the visibility of its specific impacts is helpful
RBS2.0 projects that WA’s stock of appliances will continue to rise through to 2040, alongside growth in dwellings quantities. Cooking and water heating electricity consumption per dwelling is projected to remain relatively stable, with moderate reductions in space heating and other general appliances. Reductions equate to 17% of appliance electricity consumption per dwelling between 2020 and 2040.
Corroboration
RBS2.0 is considered an exhaustive analysis and already utilises all reasonable data sources in its method. In particular, Australia’s Greenhouse and Energy Minimum Standards regulations (GEMS), which are responsible for setting requirements for energy performance for appliances, are included in the RBS2.0 methodology.
Construction Material Pathways
Steel
Objective & Approach
Define the projected emissions intensity of steel.
Projected intensities can be combined with current or projected typical quantities to define overall emissions.
Applies To Steel
Primary Source IEA (IEA, 2020)
Type Projection
Limitations
• Global study with high-level projections but considers multiple scenarios to capture some uncertainty.
The IEA (IEA, 2020) has developed a range of scenarios for the emissions intensity pathway for steel. Scenarios are separated by their respective Technology Readiness Levels (TRLs). For simplification, this study groups TRLs as below to represent three trajectories:
1. Stated Policies
2. Mature & Early Adoption
3. Prototype & Demonstration
IEA provides projections for the total emissions (Gt CO2e) and total demand (Gt). From this, the emissions intensity (t CO2- e) is calculated.
Corroboration
CSIRO also projects steel pathways under their CRD scenario (CSIRO, 2023b). This scenario projects a more ambitious reduction in emissions intensity beyond any of the IEA scenarios.
BlueScope Steel is an Australian steel manufacturer, and their 2023 Sustainability Report (BlueScope Steel, 2023) presents an emissions trajectory that aligns strongly with IEA scenarios 1 and 2. While this strategy may be uncertain, the strong alignment and the direct Australian context of this trajectory warrant its consideration.
Cement & Concrete
Objective & Approach Define the projected emissions intensity of cement/concrete.
Projected intensities can be combined with current or projected typical quantities to define overall emissions.
Applies To
Cement & Concrete
Primary Source VDZ (VDZ, 2021)
Type Projection
Limitations
• The level of import/export of Australian-produced cement places a large uncertainty over future emissions intensity projections
VDZ’s decarbonisation pathway (VDZ, 2021) for Australian cement provides two main sets of values:
1. 2050 Volume forecast
a. Increasing concrete demand
b. Decreasing cement and clinker demands due to structure design and concrete production innovations
c. Decreasing emissions factor of clinker
2. 2050 decarbonisation roadmap, detailing opportunities for emissions reductions across the value chain.
Decarbonisation opportunities are challenging to verify and less certain; thus, this study focuses on #1.
2050 demand for concrete is projected to increase by 40% over 2020 demand. However, the projected reduction in the clinker emissions intensity of 11% combined with a total clinker demand reduction of 31% (improvements in clinker/binder factor and innovations to reduce total binder demand) provides an effective total reduction in the concrete emissions intensity of 39% by 2050.
Corroboration
CSIRO also projects cement / concrete pathways under their CRD scenario (CSIRO, 2023b) and the IEA (IEA, 2023). Both alternative trajectories are broadly aligned with VDZ, though it is noted that there is some inconsistency in how the reports relate concrete vs. cement emissions intensity reductions. VDZ differentiates the relationship clearly.
Other materials
Additional construction materials may play a role, but finding a robust source for decarbonisation trajectories has been challenging. Summaries for each are provided below.
Brick
No robust trajectory could be identified; thus, the only source for any trajectory is from businesses with emissions reduction commitments. Brickworks LTD (Australia) commit to a 15% reduction in Scope 1 and Scope 2 emissions by 2030 (Brickworks, 2024). CSR LTD (Australia) also have a 30% reduction by 2030 target.
While a helpful reference, this is not recommended as an emissions pathway.
Wood
Wood presents an interesting opportunity due to its potential as a low-carbon building material. Timber emissions intensity can broadly be expected to vary by source and distance travelled rather
than by factors for the material itself. Although no trajectory could be identified, an approximate emissions reduction could be mapped alongside the emissions intensity of construction and heavy vehicle transport. This has not been included in this study.
Trends and trajectory for sawn wood consumption were identified through a Forest & Wood Products Australia report (Forest & Wood Products Australia, 2022), suggesting an increase of 56% from 2020/2030 to 2050/2060. Housing demand projections from the same report were used to calculate a trajectory of a 9.4% increase in sawn wood consumption per dwelling by 2050.
Finishes
Emissions trajectories for finishes, including plaster, paint and carpet, could not be identified.
SWIS Decarbonisation
SWIS renewable penetration and the resulting grid electricity emissions factor were projected based on reaching 60% renewable penetration by 2030 (DISER, 2022) and onwards to an estimated (based on approximate linear trajectory) 90% by 2050. This has also been compared with RBS2.0’s dataset for WA electricity supply (including both SWIS and NWIS). Although the trajectory varies (60% of renewables will front-load the transition before 2030), the 2050 outcomes are broadly aligned as the emissions factor trends towards zero.
Integrating LCA into Construction Regulations
Trends for regulated lifecycle analysis approaches in construction were reviewed to indicate how this is developing in other areas. This area cannot be determined quantitatively and may not be practical to use directly in the study, but a qualitative review is provided to help with context for this report or subsequent work in this area.
Nordic Countries
There is some initial indication that the integration of LCA approaches into construction regulation is growing, with evident leadership from the Nordic countries as per the summary below (Nordic Sustainable Construction, 2023):
• Denmark, Norway and Sweden have enforced mandatory LCA elements since 2023, 2023 and 2022 respectively.
• Estonia and Finland have a mandatory LCA plan with enforcement, reportedly beginning in 2025.
• Iceland is currently developing a similar approach.
Modules included in the mandatory LCA are shown in Table 1, with product, transport, construction process, and replacement being common across all countries (including planned updates).
Maintenance, operation energy, deconstruction, waste, disposal and recycling are present but not consistently mandated.
Rest of Europe
In Europe, the Energy Performance of Buildings Directive (EPBD) is undergoing revision towards a 2025 update (World Green Building Council, 2024), requiring that “life cycle GWP is calculated and disclosed via Energy Performance Certificates” for:
• All new buildings with a useful floor area larger than 1000m2 by 2028
• All new buildings (regardless of size) by 2030
Under this pending revision, the product, construction process, use and end-of-life stages are all included.
X = included in the regulation, O = planned but not in force yet
Table 1. LCA Modules Mandated in Construction (Nordic Sustainable Construction, 2023)
Emissions from Timber
Details on the limited development of wood products in construction are presented in Section 0 However, various factors are essential to review regarding the use of wood and timber in construction and the relevance of timber’s common claims towards carbon negativity. These factors are summarised in the following sections.
Carbon Negative Timber
It is well understood that trees and forests behave as carbon sinks. Through photosynthesis, trees absorb CO2 and turn it into carbon-based sugars, which are stored in tree branches, roots and surrounding soils. Around half the dry weight of a tree is carbon (Timber NSW, n.d.). Large proportions of this carbon remain “locked up” in the wood for its life until it decomposes, and the carbon is released into the atmosphere via CO2.
Timber products retain this stored carbon (biogenic carbon) and are generally considered carbonnegative, i.e., they store more carbon than they emit. There will typically be wasted material during timber processing, which would be a loss of some stored carbon, but the majority of carbon remains stored in the mass of the timber product. For every tonne of dry timber produced, 1.8-1.9 tonnes of CO2-e is sequestered (P. Van Der Lugt, 2020; Timber NSW, n.d.).
However, the realisation of carbon-negative benefits relies on various factors, the most relevant of which are summarised below:
1. Sustainable production and procurement: Emissions generated during the timber production phase and any emissions from associated transport will impact the total effective carbon sequestration of any given unit of timber. The production phase emissions are likely small compared to the absorbed CO2 during a tree’s growth (P. Van Der Lugt, 2020), but transport emissions may vary greatly depending on where the timber is sourced from , mainly if imported into Australia from overseas.
2. End-of-life management: When timber products reach their end-of-life, there are various options for management (dependent on the quality and any treatment process applied to the timber):
a. Landfill – causes decomposition, and stored carbon is emitted as CO2. Landfill is not a valid method if carbon is to be sequestered, and it effectively eliminates carbonnegative benefits.
b. Recycling mulch also leads to decomposition, though it is marginally more favourable than landfilling. This option should be avoided to maximise carbon-negative benefits.
c. Recycling, Timber Products – Secondary timber products such as MDF or particleboard effectively extend the wood's lifecycle and retain the stored carbon for an additional period.
d. Biomass Energy – Discarded timber products can be combusted to generate energy. Biomass energy is often considered zero-emissions, but the impact on the carbon negativity of the timber and the allocation of emissions would require further analysis.
3. Standards: Sustainability and ethical standards for timber are essential to avoid illegal logging activities. Illegal logging can lead to increased deforestation, leading to a net loss of carbon storage.
Benefits and potential negative emissions from biogenic carbon cannot be considered unless the system boundary includes production/procurement and end-of-life management.
Confidence Item Description
Notes
4.1 EV Fleet Share Projection High Australia-specific Robust dataset
4.2 Vehicle Emissions Intensity Projection High Based on regulation
4.3 VKTs Projection
4.4 Construction Vehicles and Equipment Both Moderate Some very broad assumptions, a single source of data for emissions trajectory
5.1 NG Transition Projection High Well-developed dataset, conservative pathway
5.2 Hydrogen NG Blend Strategy Moderate
5.3 Appliance Energy Efficiency Projection High Well developed dataset
6.1 Steel Projection High Multiple aligned sources
6.2 Concrete/Cement Projection High Multiple aligned sources
Cerclos. (2023). UDIA WA and Industry Partners Land Development Infrastructure Life Cycle Assessment Study
CSIRO. (2023a). Electric vehicle projections 2023: Update to the 2022 projections report CSIRO. (2023b). Pathways to lowering emissions for Australian industries. CSIRO. https://www.csiro.au/en/news/All/Articles/2023/December/pathways-net- zero-report Department of Transport. (2023). Western Australian Electric Vehicle Analysis Summary DISER. (2022). Australia’s emissions projections 2022. DISR. (2024, May). Future Gas Strategy | Department of Industry Science and Resources [Strategy or plan]. Https://Www.Industry.Gov.Au/Node/93472. https://www.industry.gov.au/publications/future-gas-strategy
DITRDCA. (2024). Cleaner, Cheaper to Run Cars: The Australian New Vehicle Efficiency Standard DJTSI. (2024, January 30). Western Australian Renewable Hydrogen Strategy and Roadmap. https://www.wa.gov.au/government/publications/western-australian-renewable-hydrogenstrategy-and-roadmap
DWER. (2023). Sectoral emissions reduction strategy for Western Australia Energy Consult. (2020). RBS2.0 Methodology Report. Forest & Wood Products Australia. (2022, August 1). Future Market Dynamics And Potential Impacts On Australian Timber Imports – Final Report Forest & Wood Products Australia https://fwpa.com.au/report/future-market-dynamics-and-potential-impacts-on-australiantimber-imports-final-report/
IEA. (2020, October). Iron and steel sector direct CO2 emission reductions by current technology maturity category in the Sustainable Development Scenario, 2019-2050 – Charts – Data & Statistics. IEA. https://www.iea.org/data-and-statistics/charts/iron-and-steel-sector-directco2-emission-reductions- by-current-technology-maturity-category-in-the-sustainabledevelopment-scenario-2019-2050
Lendlease. (2022, May 18). Stepping Up the Pace: Fossil Fuel Free Construction https://www.lendlease.com/au/insights/stepping-up-the-pace-fossil-fuel-free-construction/ McKinsey. (2021). Road Freight Zero: Pathways to faster adoption of zero-emission trucks https://www.mckinsey.com/industries/automotive-and-assembly/our-insights/road-freightglobal-pathways-report#/
National Transport Commission. (2023). Carbon Dioxide Emissions Intensity for New Australian Light Vehicles 2022 [Information Paper].
Nordic Sustainable Construction. (2023). The Operating Environment of Building LCA and BIM in the Nordics and Estonia.
P. Van Der Lugt. (2020). Carbon Storage Utilising Timber Products.
Smith, D. A., Whitehead, J., & Hickman, M. (2022). Planning a Transition to Low and Zero Emission Construction Machinery.
Timber NSW. (n.d.). Timber in the Carbon Economy. Campaign: Timber in the Carbon Economy Retrieved October 28, 2024, from https://timbernsw.com.au/timber-in-the-carbon-economy/ VDZ. (2021). Decarbonisation Pathways for the Australian Cement and Concrete Sector. World Green Building Council. (2024). Life cycle Global Warming Potential in the Energy Performance of Buildings Directive
uwa.edu.au
Appendix B
Building Envelope Emissions Calculation
Methods
This research used eTool to calculate cradle-to-gate emissions for building envelopes. The aim was to simulate several scenarios, including current practice and hypothetical future best practice.
Cradle-to-gate includes the creation of building materials, their transport to the building site, and emissions from construction. This corresponds to stages A1 – A5 as defined by the international standard1. These stages were analysed as the study primarily is focussed on possible emissions reductions from the planning and design phases of development.
The building envelope includes four constituent parts:
• Ground floor
• Upper floor (if applicable)
• External Walls
• Roof
Three different ‘cases’ were created. Each case represents a different scenario for choice of building materials.
• Baseline
• Australian Average
• Lightweight
The Baseline case was created using building permits from Jindalee, collected from the City of Wanneroo during Phase 1. It was found that almost all residences had the same envelope materials.
The Australian Average case was created using data collected by CSIRO from the Nationwide House Energy Rating Scheme’s (NatHERS) Universal Certificates2. The Universal Certificate is an assessment pathway most new dwellings in Australia use to comply with the energy efficiency requirements in Australia’s National Construction Code. The database is updated monthly so presents very current data.
The CSIRO data presents the proportion of newly constructed houses that use different building materials3. This data is broken down by building class, state or territory, and year. Data was taken for Class 1 houses, which includes both attached and detached single-resident dwellings4. This covers most of the typologies studied.
Using this data, the Australian Average case was created by taking the most common building materials used in new constructions Australia-wide.
The Lightweight case was created using a realistic best practice for envelope materials and represents the possible global warming footprint if sustainable materials are used.
A summary of the materials for each case is provided in Table 1.
Table 1: Constituent envelope materials of simulation cases
For each building material appropriate eTool templates were found or created. Any parts of the template not relating to the envelope (e.g. internal finishings) were removed. Any carbon effects from the use and end-of- life stages were not counted.
The typologies from Phase 1 were used. In that phase, average areas for the floors, walls and roof were calculated for each typology. A summary of the typologies can be found in table 2, with more detailed information available in the Phase 1 report. By using the materials from the cases and quantities from the typologies, a simulation of each typology in each case was made.
Table 2: Overview of typologies
Results
Typology 4 GWP (kg CO 2 equivalent)
Typology 5 GWP (kg CO 2 equivalent)
Typology 6 GWP (kg CO 2 equivalent)
Typology 7 GWP (kg CO 2 equivalent)
Typology 8 GWP (kg CO 2 equivalent)
External
Roof building material for new constructions (% dwellings). From CSIRO data.
Conclusion
As established in Phase 1, emissions from envelope materials essentially scale with gross floor area.
The Baseline case was worse than the Australian Average case in terms of emissions intensity. Since data collected from new developments showed that houses had very little variation in building materials, it is reasonable to assume that WA envelopes are using more emissions intensive materials than other parts of Australia. However, the difference is relatively small compared to what could be saved in a best-case scenario.
Using timber as a replacement building material confers huge emissions reductions, due to the fact sustainably sourced timber is a large carbon sink. In two-storey cases, negative emissions could be achieved. This demonstrates the possibility of decarbonising the built form of future residential developments, even with currently available building materials.
