Evidence-based adaptive urban design strategies for Western Australia
Housing performance in the
Acknowledgement
This research is supported by the Western Australian Planning Commission (WAPC), the Department of Planning, Lands and Heritage (DPLH), Development WA, the Department of Housing and Works (DHW) and the Water Corporation. The research is also supported by WA Local Governments - the City of Karratha, the City of Greater Geraldton, the Shire of Toodyay, the City of Wanneroo, the City of Cockburn, the City of Vincent, and the City of Perth.
1. Executive summary
1.1 Objectives
The specific objective of the current Phase (Phase 1) of research is to:
• Benchmark the performance of selected urban precinct and housing case studies across WA’s climate regions.
Subsequent phases will:
• identify changes between the current and likely future performance of urban precinct and housing case studies due to climate change;
• develop and evaluate the performance of design proposals to adapt urban precinct and housing case studies to projected climate change; and
• develop principles for adaptation of WA urban precincts and housing.
This report summarises Phase 1 of the project with respect to housing performance in the existing climate.
1.2 Methods
The approach taken in this research is to characterise the general performance of housing across the Western Australian climate regions through the selection and modelling of typical traditional and contemporary housing in selected case study precincts.
1.2.1
House selection
The initial selected case study sites have been chosen with the Partner Organisations to represent cities/towns within WA’s broadscale climate regions, the ‘Monsoonal North’, ‘Rangelands’, and the South-Western Flatlands. The case study sites represent typical urban forms in Broome, Karratha, Geraldton, Toodyay, and Perth’s central, eastern, and coastal areas. Individual houses were selected from Broome and Perth to represent both traditional and contemporary forms of housing in the other case studies across the state.
Northern regions: Broome and Karratha
Traditional house
• Based on a Department of Housing and Works three-bedroom traditional detached house in the old centre of Broome.
Contemporary house
• Based on a recently constructed two-bedroom new detached Department of Housing and Works house in Broome North.
Midwest and southern regions: Geraldton, Toodyay and Perth
Traditional house
• Based on an older traditional 1950s two-bedroom detached house owned by the Department of Housing and Works at 8 Upton Street, Saint James
Contemporary house
• Based on a new large four-bed display home at 7 Rottnest Street, Bushmead
1.2.2 Building energy modelling
This research element aims to establish typical housing typologies' thermal performance and energy demand using the EnergyPlus building energy modelling (BEM) software with input weather data produced by CSIRO for the chosen locations.
Each of the selected houses were modelled in EnergyPlus and the models calibrated against data obtained from instrumentation during typical summer conditions. The two houses in the Broome study sites were instrumented during a site visit between January 19th and January 26th 2024. The Department of Communities arranged access to the houses, one in Broome North and the other in old Broome. The Perth houses were instrumented during January and February 2025.
The calibrated models were then used to simulate the thermal performance of houses in the selected climate zones. The simulated performance of unconditioned modes of operation is reported for each month of the year as:
• the hourly average air temperatures in living areas; and
• the percentage of hours that living space air temperatures either exceed the cooling setpoint or are lower than the heating setpoint.
The performance of conditioned modes of operation are reported as:
• The monthly energy consumption required to achieve the cooling and heating setpoints for the location.
The assumptions about housing operation and cooling and heating setpoints from NatHERS 1 were broadly adopted for the simulations.
1.3 Findings
1.3.1
Passive performance of housing
The performance of unconditioned houses is particularly important for social housing and vulnerable families that do not have the benefit of air-conditioning. In summary, the findings of the research are:
• Unconditioned case study houses in Broome and Karratha have living area air temperatures beyond the cooling setpoint (27°C) for nearly all hours of the day and night from November to March. There is little difference in thermal comfort between the traditional and new houses.
• In Geraldton, between January and March, living area air temperatures exceed the cooling setpoint (25°C) for approximately half of the daytime and nighttime hours for both housing types.
• In Toodyay, during December to February, the living area air temperatures in the older house exceed the cooling setpoint (26°C) for approximately 80% of the daytime and nighttime hours, while in the newer house, this occurs for 50-60% of the time.
1 Nationwide House Energy Rating Scheme
• In the Perth central and eastern case studies, the houses exceed the cooling setpoint for around 50% of daytime and nighttime hours in December – February.
• In the coastal Perth case studies, the unconditioned houses exceed the cooling setpoint for 3050% of daytime and nighttime hours in December–February for both housing types.
1.3.2 Thermal energy demand of housing
The cost of electricity is an important element of household expenditure and is likely to rise as temperatures increase under climate change. Also, increasing summer demand is an important consideration for electricity providers in planning for climate change. In summary, the findings of the research are:
• Cooling energy demand on a per m2 basis is around three times as high in the Broome and Karratha case study houses compared to the central and eastern Perth houses.
• Cooling energy demands on a per m2 basis in coastal Geraldton are somewhat higher than Perth central and eastern, and somewhat higher again in inland Toodyay.
• The coastal areas of Perth have significantly lower cooling energy demand than the Perth central and eastern case study areas.
• There is little difference between the cooling energy demand of older and newer houses on a per m2 basis.
• The much larger new house type in the southern regions means that overall cooling demands per house are around three times those of smaller houses.
• Winter heating demand is negligible in the north of the state but significant in the southern regions. Heating demands are around half of the cooling demands on a per m2 basis.
• The older house types with (assumed) lower levels of airtightness have somewhat higher heating energy demand on a per m2 basis but lower overall due to size.
1.3.3 The effect of humidity
Humidity and, therefore, wet bulb temperatures are much higher in the northern regions of Western Australia, particularly in the hotter months. Air-conditioning systems both remove moisture from the air (latent cooling) and energy from the air (sensible cooling). In Broome, the latent cooling energy represents 30% of the annual cooling demand, while in Perth, the value is 16%.
1.4 Outcomes of research
The purpose of the house selection and energy modelling is to establish a benchmark for the thermal performance of typical traditional and contemporary housing across Western Australia. In the next phase of the research, the likely future performance under various climate change scenarios will be simulated using the calibrated models described in this report.
Accordingly, the important outcomes from this phase of the research are:
• The establishment of confidence in the models through calibration and comparison with actual electricity data.
• The development of an understanding of the thermal performance of houses in all regions with and without air conditioning, and
• the setting of benchmarks in all regions for the thermal energy demand (particularly cooling) for typical housing types.
2. Introduction
2.1
Future Climate Future Home objectives
Through a rare collaboration between experts in urban, landscape and architectural design, public health, climate science, engineering and climate, energy and water modelling, this project aims to:
Generate evidence to inform solutions and policy decisions concerning the climate change adaptation of urban precincts and housing to projected temperature and rainfall changes and foster healthy and climate-resilient communities across WA’s climate regions.
The specific objective of the current Phase (Phase 1) is to:
• Benchmark the performance of selected urban precinct and housing case studies across WA’s climate regions concerning Urban Heat Island (UHI) effects, thermal comfort of the outdoor environments, Thermal performance of housing, and irrigation demands for public and private open spaces (Phase 1)
Subsequent phases will:
• Identify changes between the current and likely future performance of urban precincts and housing case studies due to climate change-induced variations in temperature and rainfall (Phase 2).
• Develop and evaluate the performance of design proposals to adapt urban precinct and housing case studies to projected climate change using micro-climatic, building energy, and water modelling and community engagement (Phase 3)
• Develop CSUD principles for adaptation of WA urban precincts and housing to temperature and rainfall changes for inclusion in the revision of future state and local government policies and design guidance (Phase 4).
2.2 The thermal performance of housing
This report summarises Phase 1 of the project with respect to housing performance in the existing climate. The microclimate inside houses is a complex environment in which the physical form of the building (size, shape, construction materials, glazing, foundations, airtightness) interacts dynamically with the following variables to produce an indoor environment :
• Weather (solar radiation, air temperature and humidity, wind speed and direction);
• Local environment (shade, terrain, adjacent surfaces, obstructions to wind); and
• Operation of the house by occupants;
• Heat energy emitted by people, appliances and lighting;
The thermal performance of the unconditioned indoor environment from the perspective of human thermal comfort is characterised by several variables:
• Air temperature;
• Humidity;
• The mean radiant temperature of internal surfaces.
All of these variables are affected by air movement. Air-conditioning modifies the natural indoor environment through the removal or introduction of warm air. Both the natural performance (known
as the “free-running” mode and the conditioned mode (requiring energy) of house operation are important metrics reported here.
The approach taken in this research is to characterise the general performance of housing across the Western Australian climate regions through the selection and modelling of typical traditional and contemporary housing. In this first phase of the research, houses are modelled in the existing climate conditions. In the next phase, the modelling will incorporate likely future weather under various climate scenarios for Western Australia.
2.3 Companion reports
This report is one of a suite of documents prepared for Phase 1 of Future Climate Future Home:
• Housing performance report (this document)
• Precinct climate performance report
• Water Corporation precinct climate performance report
• Partner organisation engagement report
2.4 Project governance
This project capitalises upon a long-term successful research collaboration with four partner organisations: The Western Australian Planning Commission (WAPC), the Department of Planning, Lands and Heritage (DPLH), Development WA, and the Department of Housing and Works (DHW)
The project also forges new collaborations with the Water Corp oration, CSIRO and WA Local Governments - the City of Karratha, the City of Greater Geraldton, the Shire of Toodyay, the City of Wanneroo, the City of Cockburn, the City of Vincent, and the City of Perth. Project coordination and reporting occur through biannual Partner Organisation meetings. Project updates will also be provided to AUDRC’s Advisory board, which comprises Emma Cole – Chair of the WAPC; Anthony Kannis– Chair of DPLH; Dean Mudford – CEO of Development WA, and Leon McIvor – DirectorGeneral of the DHW and the Urban Design Research and Education Committee, which includes officer-level staff from the State Government Partner Organisations.
3. Methods
The objective for phase 1 is to benchmark the performance of selected urban precinct and housing case studies across WA’s climate regions concerning UHI effects, thermal comfort of the outdoor environments, thermal performance of housing, and irrigation demands for public and private open spaces. The focus of this report is the thermal performance of housing.
3.1 The case study precincts
3.1.1
Selection
The initial selected case study sites have been chosen with the Partner Organisations to represent cities/towns within WA’s broadscale climate regions, the ‘Monsoonal North’, ‘Rangelands’, and the South-Western Flatlands (see Table 1). The Southern and South Western Flatlands Natural Resource Management Region (NRM) is characterised by a Mediterranean-type climate, with warm, dry summers and cooler, wetter winters (Climate change in Australia, 2017). The Rangelands cluster region covers much of the Australian interior. Rainfall systems vary from seasonally reliable monsoonal influences in the north to very low and variable rainfall patterns in much of the centre and south (Climate change in Australia, 2017). The Monsoonal North NRM extends across the entire Australian continent from the Burdekin River in Queensland to the Fitzroy Basin in WA and comprises most of Australia’s dry tropical savanna (Climate change in Australia, 2017) The selected urban precinct case study sites have also been chosen to reflect:
• Established urban areas
• Contemporary best practice precincts developed or earmarked for development
• Varying urban and open space morphologies (e.g., New Urbanism, Climate Sensitive Urban Design)
Table 1: The case study precincts
Case study Natural Resource Management region Urban morphology Local Gov partner State Gov partner Status Policy relevance
Broome North Monsoonal north Compact suburb Shire of Broome DevWA
Broome traditional suburb Monsoonal north Traditional suburb Shire of Broome DHW
Bulgarra, Karratha Rangelands Radburn suburb City of Karratha DHW
Karratha town centre Rangelands Medium density precinct City of Karratha DevWA
Maitland Park Geraldton Southern and southwestern flatlands Park and schools City of Greater Geraldton
Toodyay, River Hills Estate Southern and southwestern flatlands Traditional main street/ suburb Shire of Toodyay DPLH/ WAPC
Established/ planned Broome North Waranyjarri Estate Design Guidelines
State Planning Policy 7.3- Residential Design Codes
The Broome North Structure Plan
The Kimberley Vernacular Handbook
State Planning Policy 7.0 Design of the Built Environment
Established/ planned Shire of Broome Local Planning Strategy
State Planning Policy 7.3- Residential Design Codes
State Planning Policy 7.0 Design of the Built Environment
Established State Planning Policy 7.3- Residential Design Codes
The City of Karratha Local Planning Strategy
The Pilbara Vernacular Handbook
State Planning Policy 7.0 Design of the Built Environment
Established/ planned The City of Karratha Local Planning Strategy
State Planning Policy 7.2 - Precinct Design
State Planning Policy 7.0 Design of the Built Environment
Established/ planned Maitland Park Concept Masterplan Report
Broader planning for the precinct is encompassed in the City of Geraldton Local Planning Strategy.
State Planning Policy 7.2 - Precinct Design
State Planning Policy 7.3- Residential Design Codes
Volume 2 - Apartments
Public Parkland Planning & Design Guide
State Planning Policy 7.0 Design of the Built Environment
Established/ planned Shire of Toodyay Local Planning Strategy
Liveable Neighbourhoods
State Planning Policy 7.3- Residential Design Codes
Jindalee Southern and southwestern flatlands Compact suburb City of Wanneroo DPLH/ WAPC
Nollamara Southern and southwestern flatlands Infill suburb - DHW
Leederville town centre Southern and southwestern flatlands Mediumdensity precinct/ TOD City of Vincent DPLH/ WAPC
State Planning Policy 7.0 Design of the Built Environment
Established Liveable Neighbourhoods Policy
Residential Design Codes Volume 1 for single houses and group dwellings below R60
State Planning Policy 7.0 Design of the Built Environment
Established State Planning Policy 7.3- Residential Design Codes
The City of Stirling Planning Scheme No. 3
State Planning Policy 7.0 Design of the Built Environment
Planned State Planning Policy 4.2 Activity centres
State Planning Policy 7.2 - Precinct Design
State Planning Policy 7.0 Design of the Built Environment
Central Perth Southern and southwestern flatlands Medium to high-density precinct City of Perth - Established State Planning Policy 7.2 - Precinct Design
State Planning Policy 7.3- Residential Design Codes
Volume 2 – Apartments
State Planning Policy 7.0 Design of the Built Environment
Karawara, South Perth Southern and southwestern flatlands Radburn suburb - DHW
Cockburn Central Southern and southwestern flatlands Mediumdensity precinct/ TOD City of Cockburn DHW
Established Liveable Neighbourhoods policy
State Planning Policy 7.3- Residential Design Codes
State Planning Policy 7.0 Design of the Built Environment
Established/ planned State Planning Policy 4.2 Activity centres
State Planning Policy 7.2 - Precinct Design
State Planning Policy 7.3- Residential Design Codes
Volume 2 – Apartments
Design guidelines for Cockburn Central West
State Planning Policy 7.0 Design of the Built Environment
Salt Lane Southern and southwestern flatlands Medium density precinct City of Cockburn DevWA
Established/ planned State Planning Policy 7.2 - Precinct Design
Cockburn Coast Design Guidelines for Robb Jetty and Emplacement
State Planning Policy 7.0 Design of the Built Environment
3.1.2 Wet bulb temperature variations across the case studies
Both air temperature and humidity have a significant effect on human thermal comfort. Their combined impact is captured by the wet bulb temperature (WBT). The WBT is relevant as a measure of the ability of the human body to cool through the evaporation of moisture (sweat) from the body. When the WBT exceeds skin temperature (circa 35°C), this process becomes less effective, and heat will accumulate in the body (Bolleter et al., 2021; Coffel et al., 2017).
The differences across the state concerning WBT are significant, as illustrated (see Figure 1 and Figure 2), highlighting the impact of heat and humidity in the north of the state during the summer months.
3.2 House selection
Individual houses were selected from Broome and Perth to represent both traditional and contemporary forms of housing. These case study houses were then modelled for their performance in the case study precincts across the state
3.2.1 House types for Northern regions: Broome and Karratha
Traditional house
Based on a Department of Housing and Works three-bedroom traditional detached house in the old centre of Broome at 8/18 Barker St, Broome (see Figure 3 and Figure 4). Photos of the house are set out in the Appendix.
Construction material: timber stud frame, external and internal walls clad with asbestos sheeting material. The roof is framed with timber rafters, battens, and ceiling joints. The roof is clad with asbestos cement corrugated roof sheeting.
Figure 1 Wet bulb temperature summer variation
Figure 2 Wet bulb temperature diurnal variation
Contemporary house
Based on a recently constructed two-bedroom new detached Department of Housing and Works house in Broome North at 11A Nakamura Ave, Bilingurr See Figure 5 and Figure 6 Photos of the house are set out in the Appendix.
Construction material: Steel stud frame external and internal walls clad with Colorbond sheeting material with R2 batts in external walls and R1.5 bulk installation for internal walls. The roof is steelframed with Colorbond cladding and weatherboard, and features R3 batts insulation for the ceiling and 750 mm roof eaves.
Figure 3: Barker St: Aerial image
Figure 4: Barker St- floor plan
3.2.2 House types for the mid-west and southern regions: Geraldton, Toodyay and Perth Traditional house
Based on an older traditional 1950s two-bedroom detached house owned by the Department of Housing and Works at 8 Upton Street, Saint James. See Figure 7 and Figure 8. Photos of the house are set out in the Appendix.
Construction materials: cavity brick external walls and tiled roof, with a suspended timber floor supported by limestone blocks.
Figure 5: Nakaumura Ave – aerial image
Figure 6: Nakamura Ave - Floor plan
Figure 7 Upton St - aerial image
Figure 8 Upton St - floor plan
Contemporary house
Based on a new large four-bed display home at 7 Rottnest Street, Bushmead See Figure 9 and Figure 10. Photos of the house are set out in the Appendix.
Construction material: external cavity brick wall, single brick for internal wall, corrugated iron roof, insulated ceiling with R-value of 4.1.
Figure 9 Rottnest St - aerial image
Figure 10 Rottnest St – floorplan
4. Building performance modelling
This research element aims to establish typical housing typologies’ thermal performance and energy demand using building energy modelling (BEM) software.
Energy Plus is a whole-building energy simulation program that models the response of buildings to climatic conditions, including the calculation of internal thermal conditions and energy consumption (EnergyPlus, 2024). EnergyPlus is funded by the U.S. Department of Energy’s (DOE) Building Technologies Office (BTO) and managed by the National Renewable Energy Laboratory (NREL).
All BEM software relies on weather files (epw files), developed initially for EnergyPlus but now widely used. CSIRO has produced a dataset of ‘Typical meteorological year weather files in epw format’, which comprises one year of weather data in hourly intervals for one of 83 Australian locations. The dataset is based on weather files developed for the Nationwide House Energy Rating Scheme (NatHERS) residential building simulation tools. The typical meteorological year weather dataset is based on historical weather data drawn from 1990 to 2015 using the method described by the New Zealand National Institute of Water and Atmospheric Research (NIWA). These files have been used for this study’s ENV-met and BEM modelling.
Each of the selected houses was modelled in EnergyPlus, and the models were calibrated against data obtained from instrumentation during typical summer conditions. The two houses in the Broome study sites were instrumented during a site visit between January 19 and January 26, 2024. The Department of Housing and Works arranged access to the houses, one in Broome North and the other in central Broome. The Perth houses were instrumented during January and February 2025. Details of the instrumentation and model calibration are set out in Appendix A.
The EnergyPlus simulations incorporate heat transfer between the house and the ground using a finite element calculation via the “Site:GroundDomain:Slab” subprogram. The thermal energy required to achieve setpoints in the “conditioned” simulations utilises the EnergyPlus “Ideal Air Loads” subprogram. Natural ventilation was modelled using the “ZoneVentilation: WindandStackOpenArea” subprogram which partially opens operable windows when the outdoor air temperature is lower than the indoor temperature (2°C adopted for this study) and the indoor temperature is above the heating setpoint (see Table 2 below) Details of these subprograms are included in the EnergyPlus documentation.
Each of the selected houses was simulated in both unconditioned and conditioned modes.
The performance of unconditioned modes of operation is reported for each month of the year as:
• The hourly average air temperatures in living areas, and
• The percentage of hours that living space air temperatures either exceed the cooling setpoint or are lower than the heating setpoint.
The performance of conditioned modes of operation is reported as:
• The monthly energy consumption required to achieve the cooling and heating setpoints for the location.
The cooling setpoints as set out by NatHERS 2 (Table 2) were used with the exception that a figure of 18°C was used for sleeping spaces during all hours.
Table 2: NatHERS thermostat settings
Cooling setpoint Tn = 17.8 + 0.31Tm where Tn is the neutral temperature in January and Tm is the mean January ambient air temperature.
Heating setpoint 20°C
For living spaces 18°C
For sleeping spaces: 0700 to 0900 and 1600 to 2400; 15°C
The detailed results of the simulations are set out in Appendix B Table 3 sets out the basic thermal performance of each house as determined by the following variables.
Variable Definition
Cooling and heating hours
Cooling energy / m2
Total cooling energy
The percentage of hours in the year that temperatures fall outside of the cooling and heating setpoint in the living areas of the houses.
The amount of energy required to maintain temperatures to the setpoint level per m2 of conditioned area.
The amount of energy required to maintain temperatures to the setpoint level for the whole house
Table 3: Summary of house modelling results
5.2 Passive performance
The essential passive performance of the housing is illustrated by the cooling and heating hours, referred to here as “Unmet hours”. These are depicted in Figure 11 and Figure 12 for each of the housing case studies.
5.2.1 Summer conditions
There is almost no difference in the performance of traditional and new housing in respect of summer thermal comfort, save for minor differences in the Toodyay climate zone (which extends to the east of the state). As expected, the northern case study precincts perform worst with unconditioned houses having air temperatures beyond the cooling setpoints for nearly all hours of
the day and night from November to March in both Broome and Karratha. Summer conditions are similar in the southern regions, with Perth slightly cooler than Geraldton and Toodyay and the coastal regions of Perth slightly cooler than away from the coast.
5.3 Winter conditions
Winter conditions in the northern region are comfortable, so no heating is required. Winter thermal comfort is particularly sensitive to airtightness, and the modelling assumes that newer houses are more airtight than older houses, which is why traditional houses in the southern regions perform worse than newer houses.
5.4
Conditioned performance
5.4.1 Cooling loads
The traditional and new Department of Housing and Works houses modelled in Broome and Karratha locations are of similar size and require similar amounts of cooling energy despite differences in construction (Figure 13 and Figure 14).
Figure 13: Cooling energy per m2 - northern regions
Figure 14: Total cooling energy - northern regions
Cooling loads in the south of the state are less than half that in Broome and Karratha on a per m2 basis, but exhibit no significant differences between traditional and new houses. The results broadly reflect latitude, but with the coastal influence observable in Geraldton and Perth.
Figure 11: Unmet cooling hours
Figure 12: Unmet heating hours
The new house design represented in the southern region case studies is around the average size of new housing in Perth at 206m2 (conditioned area) compared to the traditional house (67m2 conditioned area). Accordingly, the total cooling energy is proportionally higher.
5.4.2
Heating loads
Heating loads in the northern regions are negligible, although some heating may be required in Karratha. In the south of the state, heating loads on a per m2 basis are around half that of traditional houses (due mainly to airtightness) – see Figure 17. However, that benefit is more than offset by the larger size of the new house – see Figure 18
Figure 15: Cooling energy per m2 - southern regions
Figure 16: Total cooling energy - southern regions
Figure 17: Heating energy per m2 - southern regions
Figure 18: Total heating energy - southern regions
6. Electricity demand data
The energy predictions of the models have been compared with actual electricity data for the Broome and Perth case studies.
6.1 Broome
Monthly electricity consumption statistics were obtained from Horizon Energy for the houses in the case study precincts in Broome for each month of 2022-2024.
6.1.1 Broome North
The Nakamura house is identified in Figure 19, and the median electricity use of all houses is set out in Figure 20
Figure 19: Broome North case study precinct
Figure 20: Broome North median daily electricity consumption
As there is negligible heating required in Broome, the cooling energy can be inferred from Figure 20 for comparison with the model projections set out in Section 5 (Figure 21 3).
3 The calculation assumes an Energy Efficiency Ratio (EER) of 3.5
Figure 21 Cooling energy - Broome North
The modelled cooling energy for the Nakamura house is significantly lower than the median house consumption in the precinct. As Figure 19 shows, the house is much smaller than most of the houses in the precinct, so the model predictions of cooling energy demand are consistent with the electricity consumption data.
6.1.2 Broome Central
The Barker house is identified in Figure 22, and the median electricity use of all houses is set out in Figure 23
22: Broome Central case study precinct
23: Broome Central median daily electricity consumption
The cooling energy can be inferred for comparison with the model projections set out in Section 5 (Figure 24).
This precinct represents the older part of Broome, where houses are smaller than those in Broome North, and the modelled Barker house represents the median. The electricity data support the model predictions
Figure
Figure
Figure 24 Cooling energy - Broome Central
6.2 Karratha
Monthly electricity consumption statistics were also obtained from Horizon Energy for the houses in the case study precincts in Karratha for each month of 2022-2024.
6.2.1 Bulgarra
The Bulgarra precinct is identified in Figure 23, and the median electricity use of all houses is set out in Figure 24.
25: Bulgarra case study precinct
26: Bulgarra median daily electricity consumption
The cooling energy can be inferred for comparison with the model projections for the Barker house set out in Section 5 (Figure 25).
The small Barker house is representative of the older houses in Bulgarra, but there are also several larger, newer houses. Accordingly, the modelled house can be assumed to be smaller than the median house in the precinct. The electricity data support the model predictions
Figure
Figure
Figure 27 Cooling energy – Bulgarra
6.3 Perth
Western Power services the Perth houses as part of the South West Interconnected System (SWIS). Daily average data were obtained from Western Power for all suburbs of Perth from 2018 to 2023. In addition, electricity data were obtained from the Rottnest house for the period of instrumentation. Both sets of data are included in this analysis.
6.3.1 Upton house
No direct information is available for this house, which is depicted in Figure 28. The Western Power data for the suburb of St James includes electricity imported from the SWIS and exported from rooftop solar. Using a separate in-house solar PV and battery model, the amount of self-supply and hence total electricity demand for an average dwelling was calculated for the year 2023 (Figure 29).
The total electricity demand and implied thermal energy demand are compared with the EnergyPlus modelled thermal energy in Figure 30 The EnergyPlus model accurately reflects summer cooling demands but underestimates winter heating demand, likely due to assumptions about airtightness, which significantly impacts winter heating requirements. It is also important to note that actual winter heating demands are likely to be higher than noted here, as some houses retain gas for heating, which is not included in the Western Power data.
30 Upton - EnergyPlus modelled thermal energy demand
Figure 28: Upton St house
Figure 29: St James - imported electricity
Figure
6.3.2 Rottnest house
This house is located in the eastern suburb of Bushmead (see Figure 31). The Western Power data for the local government area of Swan includes electricity imported from the SWIS and exported from rooftop solar. Using a separate in-house solar PV and battery model, the amount of self-supply and hence total electricity demand for an average dwelling was calculated for the year 2023 (Figure 32).
The total electricity demand and implied thermal energy demand are compared with the EnergyPlus modelled thermal energy in Figure 33. The EnergyPlus model accurately reflects summer cooling demands but underestimates winter heating demand, likely due to assumptions about airtightness, which significantly impacts winter heating requirements. It is also important to note that actual winter heating demands are likely to be higher than noted here, as some houses retain gas for heating, which is not included in the Western Power data.
In addition to this comparison, metered electricity data were collected during the instrumentation of the Rottnest house in February 2025. The house was unoccupied except for periods of display, mainly on weekends, and the air conditioning was used sporadically during this period 4 . Figure 34 depicts the metered electricity demand together with the average EnergyPlus projected February cooling demand and the outdoor and indoor temperatures during the instrumentation period.
4 Electricity demand outside the periods of air-conditioning was very low (0.05 kWh/day) and is subtracted from the total to illustrate likely cooling load.
Figure 31 Rottnest St house
Figure 32 Rottnest - imported electricity
Figure 33 Rottnest - EnergyPlus modelled thermal energy demand
As expected, power demand spiked whenever the air-conditioning was switched on, which is not representative of continuous operation and likely overestimates cooling demand during normal occupancy. However, the average daily cooling demand after February 5 was 13.6 kWh/day, which is very similar to the modelled average. This provides further confidence that the EnergyPlus model is a reasonable representation of the thermal performance of the dwelling.
Figure 34 Rottnest - instrumentation period energy demand
7. Conclusions
7.1 Objectives
The purpose of the house selection and energy modelling is to establish a benchmark for the thermal performance of typical traditional and contemporary housing across Western Australia. In the next phase of the research, the likely future performance under various climate change scenarios will be simulated using the calibrated models described in this report.
Accordingly, the important outcomes from this phase of the research are:
• The establishment of confidence in the models through calibration and comparison with actual electricity data
• The development of an understanding of the thermal performance of houses in all regions, with and without air conditioning
• The setting of benchmarks in all regions for the thermal energy demand (particularly cooling) for typical housing types.
7.2 Passive performance of housing
The performance of unconditioned houses is particularly important for social housing and vulnerable families that do not have the benefit of air-conditioning. In summary, the findings of the research are:
Unconditioned case study houses in Broome and Karratha have living area air temperatures beyond the cooling setpoint for nearly all hours of the day and night from November to March. There is little difference between the traditional and new houses:
• In Geraldton, between January and March, living area air temperatures exceed the cooling setpoint for approximately half of the hours for both housing types.
• In Toodyay, during December to February, the living area air temperatures in the older house exceed the cooling setpoint for approximately 80% of the hours, while in the newer house, this occurs for 50-60% of the time.
• In the Perth central and eastern case studies, the houses exceed the cooling setpoint for around 50% of hours in December – February.
• In the coastal Perth case studies, the unconditioned houses exceed the cooling setpoint for 30-50% of hours in December–February for both housing types.
7.3 Thermal energy demand of housing
The cost of electricity is an important element of household expenditure and is likely to rise as temperatures increase under climate change. Also, increasing summer demand is an important consideration for electricity providers in planning for climate change. In summary, the findings of the research are:
• Cooling energy demand on a per m2 basis is around three times as high in the Broome and Karratha case study houses compared to the central and eastern Perth houses.
• Cooling energy demands on a per m2 basis in coastal Geraldton are somewhat higher than Perth central and eastern , and somewhat higher again in inland Toodyay.
• The coastal areas of Perth have significantly lower cooling energy demand than the Perth central and eastern case study areas.
• There is little difference between the cooling energy demand of older and newer houses on a per m2 basis.
• The much larger new house type in the southern regions means that overall cooling demands per house are around three times those of smaller houses.
• Winter heating demand is negligible in the north of the state but significant in the southern regions. Heating demands are around half of the cooling demands on a per m2 basis.
• The older house types with (assumed) lower levels of airtightness have somewhat higher heating energy demand on a per m2 basis, but lower overall due to size.
7.4 The effect of humidity
As identified in Figure 1, humidity and, therefore, wet bulb temperatures are much higher in the northern regions of Western Australia, particularly in the hotter months. Air-conditioning systems both remove moisture from the air (latent cooling) and energy from the air (sensible cooling). The EnergyPlus modelling of houses in Broome (Figure 35) and Perth (Figure 36) illustrates the relative impact on cooling energy demand for similar-sized houses
In Broome, the latent cooling energy represents 30% of the annual cooling demand, while in Perth, the value is 16%
Figure 35 Broome – energy demand
Figure 36 Perth – energy demand
8. References
Bolleter, J., Grace, B., Foster, S., Duckworth, A., & Hooper, P. (2021). Projected extreme heat stress in northern Australia and the implications for development policy. Planning Practice & Research. https://doi.org/https://doi.org/10.1080/02697459.2021.2001733 Climate change in Australia. (2017). Climate change in Australia. Australian Government. Retrieved 11.05 from http://ccia2007.climatechangeinaustralia.gov.au/ Coffel, E., Horton, R. M., & De Sherbinin, A. M. (2017). Temperature and humidity based projections of a rapid rise in global heat stress exposure during the 21st century. Environmental Research, 13(014001), 3-9. https://doi.org/https://doi.org/10.1088/1748-9326/aaa00e EnergyPlus. (2024). EnergyPlus. EnergyPlus. Retrieved 13.09 from https://energyplus.net/
