Precinct climate performance report_rev A

Future Climate, Future Home

Evidence-based adaptive urban design strategies for Western Australia

Precinct climate performance in

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

The latest IPCC report on climate change contains dire projections for the impacts of climate change across Australia However, the implications of changing temperatures and rainfall on urban precincts, public open spaces and housing in WA remain poorly understood. There is a need for evidence-based strategies to underpin adaptation measures and Climate-Sensitive Urban Design (CSUD). Accordingly, the Future Climate Future Home 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 this Phase 1 report is to:

Benchmark the performance of selected urban precinct case studies across WA’s climate regions concerning thermal comfort of the outdoor environments in the current climate.

The initial (n=12) selected precinct case study sites have been chosen with the Partner Organisations to reflect:

• Established urban areas

• Contemporary best practice precincts developed or earmarked for development

• Areas of varying area-level socio-economic disadvantage and

• Differing urban and open space morphologies.

The climatic conditions in each study site were characterised through data analysis and modelling. ENVI-met modelling was undertaken for a 14-hour period on a current ‘average’ summer day for each precinct. Our ENVI-met modelling reveals that strong to extreme heat stress is evident in all case studies in the middle of an average summer day The Kimberley, Pilbara, and Wheatbelt case studies (e.g., Broome North, Bulgarra, and Toodyay) tend to experience the most pronounced outdoor heat stress We note that these case studies also tend to have populations of lower socioeconomic status, with often less capacity to adapt to increasing temperatures.

Collectively, these findings indicate some significant challenges ahead:

• The prevalence of strong to extreme heat stress in all the case study precincts indicates the need to fundamentally reimagine urban precincts for thermal comfort in summer conditions

• In almost all our case studies, thermal discomfort is most extreme in areas adjacent to clustered housing, as exemplified in background infill areas (e.g., the Perth middle ring suburb of Nollamara) or new compact suburbs (e.g. Jindalee on Perth’s fringe). This situation primarily reflects lower wind speeds and, to a lesser extent, hard surfaces (both paving and walls) re-radiating heat, as well as, in some cases, limited shade from trees. Greater attention is warranted to the arrangement and density of housing to facilitate ventilation while still increasing overall urban density.

• The lack of canopy cover in private lots, parks and streets was a factor in the levels of heat stress in our case study precincts. Moreover, the lack of urban cooling provided by many of

the parks in our case studies is also indicative of a lack of canopy cover. Fostering healthy and extensive urban forests will require reprioritising trees in the urban environment, appropriate funding for tree planting efforts, and statutory protection for tree specimens on privately owned land.

• The lower socio-economic status of some of the case studies most affected by heat stress raises questions about the ability of residents to actively adapt to climate change (rather than just attempting to cope with its effects).

In summary, strong to extreme heat stress is evident in all precinct case studies during the middle of the day, and future climate change will exacerbate this issue further. The exact nature of this worrying increase in extreme stress is the subject of subsequent stage 2 reports

Please refer to the appendices for technical details on microclimatic modelling (Appendix A-D) and current irrigation requirements (Appendix E). Other reports in this phase focus on the climate performance of housing and Water Corporation case studies.

2. Introduction

2.1 Context

Despite our comparative inaction in mitigating climate change (CC), Australia has much to lose from a changing climate The IPCC warns that ‘the region faces an extremely challenging future that will be highly disruptive for many human and natural systems’(IPCC, 2022). The damage is already evident, with extreme events, such as droughts, heatwaves, bushfires, and floods, becoming more frequent and catastrophic. Climate impacts are ‘cascading and compounding across sectors and socio-economic, and natural systems’(IPCC, 2022) and critical climate risks to Australian cities include challenges to publicly and privately-owned assets and infrastructure systems from gradual impacts like temperature rise and extreme events like floods, heatwaves and bushfires; more significant risk of human injury, disease and death, and interrupted labour force productivity, due to heat stress. Climate change will also damage ecosystems that support social well-being, provide services fundamental to our health, and offer protection from natural disasters (Australian Government, 2015)

Extreme heat puts marginalised populations, people of low socio-economic status and those living in areas with low vegetation and tree canopy at increased health risk. Extreme heat is the most dangerous natural hazard in Australia. Indeed, between 1987 and 2016, natural disasters caused 971 deaths and 4,370 injuries, with more than 50% due to heat waves. Extreme heat conditions significantly disturb people's thermoregulation, which can have severe consequences. For vulnerable groups such as children, older adults, obese people, and people suffering from heart, lung or blood pressure conditions and for pregnant women, heat stress can cause various health problems such as heat rash, heat cramps, exhaustion, dehydration, kidney failure and breathing problems (Lenzholzer, 2015, p. 23).

Moreover, excess heat load can cause significant discomfort, altering the frequency and patterns of outdoor activities and reducing the level of exercise undertaken (Sharifi et al., 2016). Indeed, during summer heatwaves, parks are frequently warmer than the thermal comfort level of humans in the majority of Australian cities, and once the temperature reaches the threshold of 28 °C, necessary and optional activities in outdoor spaces start to decline (Sharifi et al., 2016, p. 1833) The combined effects of heat stress, retreat to interior environments, and increased private vehicle use lead to higher energy consumption (Shooshtarian et al., 2020), public health impacts, and declining liveability.

2.2 Overall research 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 this Phase report is to:

Benchmark the performance of selected urban precinct case studies across WA’s climate regions concerning thermal comfort of the outdoor environments in the current climate.

2.3 Project governance

This project capitalises on 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 Corporation, CSIRO, and WA local governments, including 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 occurs 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 –Director-General of the DHW and the Urban Design Research and Education Committee, which includes officer-level staff from the State Government Partner Organisations.

3. Methods

Urban adaptation to extreme heat in WA is urgent. However, the state lacks a comprehensive analysis of the current climate performance of urban precincts throughout WA’s climate regions – to identify areas whose populations are vulnerable to heat stress and to provide a benchmark against which the impact of future climate change can be evaluated. As such, the research question for this report is:

What is the current climate performance of selected urban precinct case studies across WA’s climate regions concerning the thermal comfort of the outdoor environments?

3.1 Microclimatic modelling

Characterising the climatic conditions in each precinct study site was undertaken through a combination of data analysis and modelling. ENVI-met software (ENVI-met, 2021) was used to model the microclimatic conditions during summer for each study site (metropolitan and regional). ENVImet is a three-dimensional microclimate simulation software incorporating various scientific disciplines – from fluid dynamics and thermodynamics to plant physiology and soil science. ENVI-met simulates a specific meteorological situation for a specific planning scenario (generally the size of a neighbourhood). The horizontal resolution is typically 1-10 m, with simulated periods ranging from 1 to 5 days. ENVI-met simulations incorporate:

• Short- and long-wave radiation fluxes taking into account shading multiple reflections from surfaces, buildings, and vegetation. Advanced modelling of radiative processes in plant canopies, including scatter and diffuse reflections

• Three-dimensional representation of trees using skeletal models to simulate biomechanical loads and deformations due to wind forces. Dynamic adjustment of seasonal effects (leafless to full canopy), including detailed simulation of radiation processes within the canopy.

• Determination of evapotranspiration and sensible heat fluxes to and from plants, including full simulation of all plant physical parameters (e.g. photosynthetic rate). Simulation of feedback processes between soil moisture and plant water stress.

• Dynamic calculation of surface and wall temperatures for each facade and roof element with up to three material layers and seven dynamic calculation points in the wall. Detailed data output for advanced analysis and generation of input data for use in building energy simulation software, such as EnergyPlus.

• Consideration of façade and roof greening in relation to all energy flows. A detailed simulation of greening systems, including construction type, substrate, and plant cover properties, considers complex processes such as radiation transmission and reflection, as well as evaporation from plants and substrate.

• Simulation of water and heat exchange within the soil system. Three-dimensional heat transfer simulation as a function of soil material and water content. Advanced calculation of hydraulic water exchange in the soil, including root water uptake and plant water supply.

• Dispersion of gases and particles, considering both particulate and gaseous components. For particles, sedimentation and deposition processes are included on leaves and surfaces Gaseous pollutants can be simulated, including photochemical transformation in the NO-NO₂ozone reaction cycle.

• The BIO-met post-processor can simulate various static comfort indices, including the Physiological Equivalent Temperature (PET) and Universal Thermal Climate Index (UTCI)

• Simulation of Dynamic Thermal Comfort Calculation of transient biometeorological processes of virtual pedestrians walking through the ENVI-met model (ENVI-met, 2021)

ENVI-met software version 5.6.1 was employed for microclimatic modelling to benchmark the performance of all study sites. All buildings, surfaces, and vegetation were digitised in ArcMap 10.8.2. This involved identifying the material properties for roofs, walls, and surfaces, comparing them with the software’s default options, and creating required materials (Figure 1). The assigned IDs for the created materials were used during the digitisation process in ArcMap, resulting in the identification and creation of 17 different roof types, seven different wall types, and 11 different surface types in the project library (refer to the Digitisation Details Table in Appendix A).

Figure 1: Building, surface, and vegetation modelling in ENVI-met.

Vegetation modelling included the digitisation of grass, shrubs, and trees. As the default software library does not contain trees from the southern hemisphere, these were classified and created using the ENVI-met Albero program based on specific attributes, such as height, crown height and width, trunk height, tree calendar, and leaf type and positioning. The model was then exported through QGIS version 3.34.8. The simulation was run using the latest 2024 epw weather file (see Appendix B and C) for an average summer day, and the thermal comfort index, specifically the Physiological Equivalent Temperature (PET), was calculated using the detailed microclimate output for the study precincts.

The purpose of the Phase 1 modelling is to establish a benchmark against which the impact of future climate change can be evaluated in Phase 2. The ENVI-met modelling was undertaken for a 14-hour period on an ‘average’ summer day for each precinct as model inputs. The average day was identified by comparing the hourly dry bulb temperature, relative humidity and wind speed with the median hourly values of those variables. For the Perth case studies we used ‘average days’ for 3 different climate zones: Coastal north (e.g., Jindalee) CZ52, Coastal south (e.g., Cockburn) CZ54 and elsewhere CZ13 The graphs illustrating this analysis are presented in Appendix C. The tabled ENVI-met outputs are a snapshot (typically at 1.00 pm) of a typical summer’s day, and we acknowledge that they do not necessarily reflect other times of the day or year.

The complete set of ENVI-met outputs for each precinct is included in Appendix D. These comprise:

• An aerial image of the precinct

• weather file input data for the selected day

• Perspective images of the precinct depicting the built form and vegetation

• a map illustrating the model surface materials

• Output maps illustrating conditions at the hottest hour of the day in respect of surface temperature, PET, air temperature, wind speed and direction, and specific humidity.

A summary of the monitoring results is set out in this report.

3.1.1 Climate data

The climate analysis and inputs to the ENVI-met modelling carried out in this study are derived from so-called Representative Meteorological Year (RMY) or Typical Meteorological Year (TMY) weather files produced by CSIRO. These files incorporate hourly data taken from actual BOM datasets from the period 1990-2015 and combined to approximate a ‘typical’ year. Analysis of these files provides a snapshot of the existing weather in each project precinct. These are summarised for each location, and rainfall data is compiled from BOM datasets in Appendix B.

Figure 2 and Figure 3 below summarise the distribution of dry bulb temperature and relative humidity across the summer months 1

These illustrate the concentration of higher temperatures in Broome and Karratha compared with temperatures elsewhere. Temperature and relative humidity distributions are similar in the coastal

1 Leederville is in the general Perth climate zone (CZ13) so the graphs also represent climate conditions in Nollamara, Perth Central and Karawara. Salt Lane is also represented by the Cockburn graphs.

Figure 2: Summer dry bulb temperature distributions

Figure 3: Summer relative humidity distributions

locations of Geraldton, Jindalee, and Cockburn, with slightly larger temperature distributions and lower relative humidity away from the coast in Toodyay and Leederville.

Relative humidity in Broome and Karratha is only slightly higher than elsewhere; however, when combined with higher temperatures, it leads to elevated wet-bulb temperatures, which are a more accurate indicator of thermal comfort conditions.

Rainfall varies widely across the state (Figure 4), with most falling during the summer monsoonal months in Broome (and to a lesser extent in Karratha) and during the winter months in the southern regions. Geraldton, Toodyay, and Perth experience very little rain during the summer months. Autumn is the driest season in all regions. In the south of the state, the annual rainfall increases with latitude, as the rain-bearing cold fronts have a greater impact in the southwest, particularly near the coast.

Evapotranspiration is strongly associated with temperatures and is significant in all seasons except winter (Figure 5).

3.2 Climate and human thermal comfort

In outdoor conditions, human thermal comfort levels are influenced by several weather variables, including direct and indirect exposure to solar radiation, wind speed, and relative humidity.

Shortwave solar radiation (both direct and diffused) is received at the Earth’s surface, and some of it is reflected depending on the surface's albedo. The abundance of dark surfaces with high heat capacity (e.g. concrete) gives rise to the urban heat island (UHI) effect in built-up urban areas. The shortwave radiation absorbed by surfaces is re-radiated as longwave radiation, including by roads, buildings and trees. Direct radiant heat transfer has a significant influence on human thermal comfort in climates such as Western Australia (Merchant et al., 2022)

ENVI-met calculates the net effect of these radiation sources at each location and elevation of the modelled area. Figure 6 illustrates the results for an average summer day in an exposed region of a small park in Jindalee. The mean radiant temperature (MRT) concept reflects the impact of radiant heat transfer between a person and adjacent objects.

Figure 4 WA average rainfall

Figure 5 WA average evapotranspiration

6: Average summer day solar radiation in Perth

3.2.1 Human Thermal Comfort Indices

Outdoor human thermal comfort refers to an environmental condition where a person feels comfortable and is neither hot nor cold (Staiger et al., 2012), a mental state that expresses satisfaction with the thermal environment and one that maintains the function of the human organism from a physiological perspective (ASHRAE, 2010; Staiger et al., 2012) Outdoor thermal comfort is a crucial factor influencing the use of public spaces, such as urban parks, and is of increasing concern to climatologists and urban planners (Chen et al., 2015). Therefore, evaluating and considering human comfort is increasingly emphasised as one of the ‘final targets of environmental design’ (Murakami, 2006) and is attracting increasing research (Zhao et al., 2021)

Human thermal comfort is assessed using thermal comfort indices. Thermal comfort indices describe how the human body experiences atmospheric conditions, combining objective climatic factors with subjective human factors such as body type, activity level, and clothing (Zhang et al., 2019). Measurement of thermal comfort has traditionally been conducted through survey-based or in-field recording methods (Lai et al., 2019). However, considering meteorological, physiological, and clothing inputs in a single model to attain multidimensional quantification of outdoor environmental thermal comfort is increasingly popular, but it necessitates sophisticated calculations (Broede et al., 2012) Many indices, such as Perceived Temperature (PTJ), often fail to account for essential meteorological factors like solar radiation, wind speed, and MRT, which are critical in planning and design assessments (Fiala et al., 2012; Park et al., 2014)

Table 1 presents the most common indices explicitly designed for measuring levels of thermal comfort in outdoor environments and their associated thermal comfort performance (Golasi et al., 2016; Shooshtarian et al., 2020; Zare et al., 2018; Zhang et al., 2019). For example, a pedestrian is considered ‘comfortable’ when the physiologically equivalent temperature (PET) is 18-23. PET accounts for both shortwave and longwave radiation fluxes and their impact on body heat balance (Fischereit & Schlünzen, 2018; Morakinyo & Lam, 2016) The Outdoor Standard Effective Temperature (OUT_SET) is calculated based on two physiological parameters: skin temperature and wetness (Blazejczyk et al., 2012)

Figure

Table 1: Thermal Sensation and Thermal Comfort Indices

Thermal Comfort Indices for the outdoor environment

Approach

Physiological Equivalent Temperature (PET) Universal Thermal Climate Index (UTCI) Outdoor Standard Effective Temperature (OUT_SET) Thermal perception Grade of physiological stress

Physically based Regressionbased Physically based

Numeric Ranges

– 23 +9 to +26 (+18 to +26 Sub range for the comfortable thermal comfort zone in urban areas (Broede et al., 2012))

No thermal stress

3.2.2 The Physiological Equivalent Temperature index

This study used the PET index as a proxy for human thermal comfort in outdoor environments. The Physiological Equivalent Temperature (PET) is defined as the air temperature at which, in a typical

indoor setting (without wind and solar radiation), the heat budget of the human body is balanced with the same core and skin temperatures under the complex outdoor conditions being assessed

ENVI-met explains the PET calculation as follows:

• Define all incoming and outgoing fluxes in the human body

• Calculate a skin and a core temperature that match all the calculated fluxes

• Transpose the person into an indoor environment

• Reset all data that is not available in an indoor environment (direct solar radiation, forced wind movement)

• Search for an indoor air temperature (as the sole parameter) that yields the same skin temperature and core temperature as the outdoor setting.

• This theoretically calculated indoor temperature is referred to as PET (ENVI-met, 2021).

PET is particularly reflective of short and long-wave radiation and hence MRT, and it is significantly higher than the air temperature in Western Australia’s summer climate. In summer days, PET values may be more than 20°C higher than the air temperature under direct solar radiation (Höppe, 1999). This is important as it is the trapping of heat within the atmosphere that is increasing with global warming due to reductions in outgoing longwave radiation from the atmosphere, together with enhanced absorbed solar radiation (Donohoe et al., 2014)

The other major influence on the state's outdoor thermal comfort (PET) is the higher levels of absolute humidity in the north during the summer months. PET incorporates its effects, but the wet bulb temperature (WBT) provides a more straightforward explanation, incorporating temperature and humidity. The WBT is relevant as a measure of the human body's ability to cool through the evaporation of moisture (sweat) from the skin. 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 combined effect of WBT, radiation effects, and wind conditions determines the perceived thermal comfort that humans experience, as reflected in the PET results.

The differences across the state concerning WBT are significant, as illustrated (Figure 7 and Figure 8), highlighting the impact of heat and humidity in the north of the state during the summer months.

7 Wet bulb temperature summer variation

3.3 The case study precincts

3.3.1

Selection

The initial selected case study sites have been chosen in collaboration with the Partner Organisations to represent cities/towns within WA’s broad-scale climate regions, namely the ‘Monsoonal North’, ‘Rangelands’, and the South-Western Flatlands (see Table 2). 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 encompasses a significant portion 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). 2 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 and

• Varying urban and open space morphologies

2 More detailed information on Western Australia’s climate is available from the Bureau of Meteorology (BOM) (Bureau of Meteorology, 2019) and CSIRO’s Climate Change in Australia resource (Climate change in Australia, 2017)

Figure

Figure 8 Wet bulb temperature diurnal variation

Table 2: The case study precincts

Case study

Broome North Monsoonal north Compact suburb - DevWA Established/ planned Broome North Waranyjarri Estate Design Guidelines

Broome central Monsoonal north Traditional suburb - 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

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

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

Toodyay, River Hills Estate Southern and southwestern flatlands Suburb Shire of Toodyay DPLH/ WAPC

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

Central Perth Southern and southwestern flatlands

Medium to high-density precinct

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

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

Established/ 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

City of Perth - Established City of Perth City Planning Scheme No 2

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

Established Liveable Neighbourhoods policy

State Planning Policy 7.3- Residential Design Codes

State Planning Policy 7.0 Design of the Built Environment

Cockburn Central Southern and southwestern flatlands Mediumdensity precinct/ TOD

City of Cockburn DHW 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

3.3.2 Sourced information

Spatial information on the case studies has been drawn from multiple sources:

• Building footprints:

o ‘Ai Deep Learning’ Buildings 2023 (Landgate -468); and

o Building Footprints 2017 (Landgate)

• Cadastre 2023 (DPLH).

• Large Scale Topo Road Segment (Line) (LGATE-162)

• ‘Ai Deep Learning’ Pools 2023 (LGATE-479)

• ‘Ai Deep Learning’ Solar Panels 2022 (Landgate -481)

• Urban Forest Parcels - 2020 (DPLH-095)

Within each case study, a fine-grained analysis of building types (based broadly on morphology) was conducted Experts were contracted to identify tree species across all the case studies, and planting plans for parks and streetscapes were provided by local government authorities (where available).

4. Results

4.1

4.1.1

Precinct comparisons

Outdoor thermal comfort

The modelled heat stress for each case study are presented in Table 3 and Table 4, and the modelled air temperatures and PET values in Figure 9 to Figure 14. These illustrate the similarities and differences between the various locations concerning PET and air temperatures on an average summer day in the current climate (noting that all the case studies- even within Perth- have been modelled with slightly different climatic conditions, making direct cross-comparisons difficult).

In summary, outdoor strong to extreme heat stress, as measured by PET, is evident in all precinct case studies over the course of an average summer day, as observed in the sun in an unshaded location. It should be noted that PET reflects extended exposure of the human body to certain conditions, such as outdoor work or recreation. Strong to extreme heat stress is evident in all cases during the middle part of the day, as noted by the PET values, which reflect significant periods of outdoor exposure, such as work or recreation. Outdoor thermal comfort is significantly influenced by direct and indirect solar radiation during the middle of the day.

The Kimberley, Pilbara, and Wheatbelt case studies (e.g., Broome North, Bulgarra, and Toodyay) tend to experience the most pronounced outdoor heat stress (Bolleter et al., 2021). However, we note that the spacious layout and extensive tree canopy of the Broome Central case study, to some degree, mitigate the heat stress of Broome’s hot, humid summer.

The impact of coastal adjacency (essentially the effect of the afternoon sea breeze) is evident in Geraldton, Jindalee, Salt Lane (and Cockburn Central to a lesser extent), compared with Toodyay, Karawara and Nollamara.

The literature on Urban Heat Island (UHI) effects suggests that outdoor heat stress is likely to increase with urban density and the thermal mass of roads, car parks, pavements, and buildings (Rohinton, 2005). Indeed, the Leederville town centre, which features expansive park-and-ride car parks and substantial urban development, received a poor rating for heat stress. However, this was not always the case in our analysis. Indeed, some case studies, such as Karawara, which has a typically low density, also received poor ratings. No linear relationship exists between urban density and heat stress as measured through PET

Table 3: Strong heat stress (% of daylight hours)

Table 4: Extreme heat stress (% of daylight hours)

9:

11:

13: Air temp - Perth

10: PET – northern case studies

12:

Figure 14: PET - Perth

The following sections provide a detailed examination of the thermal conditions in each case study

Figure

Air temp – northern case studies

Figure

Figure

Air temp - Geraldton and Toodyay

Figure

PET - Geraldton and Toodyay

Figure

4.2 Broome case studies

Figure 15: Broome case studies

Climate

zone

The Broome case studies (Figure 15) are sited within the National Construction Code designated climate zone 1: High humidity summer, warm winter (Australian Building Codes Board, 2024)

Broome has a hot semi-arid climate (BSh) under the Köppen climate classification, falling just short of the rainfall needed to qualify as a tropical savanna climate (Aw). Like much of tropical Australia, Broome experiences two distinct seasons: a dry season and a wet season (Sturman & Tapper, 1996). The dry season, lasting from April to November, is marked by mostly clear skies and average maximum temperatures around 30 °C. The wet season, which runs from December to March, brings higher temperatures of around 35°C, high humidity, and unpredictable tropical downpours (Bureau of Meteorology, 2025).

Case study description

The Broome North precinct case study comprises:

• Compact suburban lots (~400-500m2) with generally moderate site building coverage.

• A fine-gridded street network with a cardinal orientation

• Public Open Space typically consists of small Local or Neighbourhood parks.

• Single-storey houses (~250m2) with Colourbond steel roofs and often walls.

• Reasonable emerging tree canopy coverage in streets and backyards (Figure 16)

The selected precinct is part of the broader Broome North project (by DevelopmentWA), which aims to cater to Broome’s long-term growth. Broome North has been designed to adhere to the principles of tropical urban design and respond to the specific nature of Broome’s climate and environmental conditions, thereby reducing heat radiation build-up during the day and maximising ventilation cooling day and night (Figure 17). The two critical environmental factors in Broome North's design are shade and breeze. These two factors have led to the following urban design responses:

• The orientation of lots is in a cardinal direction to reduce radiant solar gains through all wall areas.

4.2.1 Broome North

Figure 16: The Broome North case study precinct.

• Main arterial streets run north-south, with most lots oriented east-west, and the houses are designed to face the wind, with generous breeze paths identified on the south or east side of the lot to allow the best cooling breezes to flow through the subdivision.

• Where lots are narrower than 15m, the lot runs North-South, allowing the additional benefit of one house providing western shade to the neighbouring house.

• Smaller dwelling footprints are encouraged, as they provide outdoor living spaces and breezeways between houses (Landcorp, 2011).

Other critical Climate Sensitive Urban Design principles of the housing in the Broome North case study precinct are:

• Maximise external wall areas (plans with one-room depth are ideal) to encourage the movement of breezes through the building (cross-ventilation).

• Site buildings for exposure to breezes.

• Shade the whole building in summer and winter.

• Use reflective insulation vapour barriers.

• Ventilate roof spaces.

• Choose light-coloured roof and wall materials.

• Elevate the building to permit airflow beneath floors.

• Consider high ceilings.

• Provide screened, shaded, and insulated outdoor living areas.

• Consider creating sleep-out spaces.

• Ensure all fences within the front setback area are no higher than 1.2m and have a minimum of 80% permeability to allow airflow to pass through unobstructed. Return fences (between the house and side fence) should also be 80% permeable and no higher than 1.8m.

• Design and build for cyclonic conditions (Landcorp, 2011)

One aspect of the estate’s design criteria was maintaining access to prevailing breezes on new lots (Engawa, 2018) On behalf of Landcorp, Engawa Architects collected weather data in 2009 and 2010 to help inform the subdivision design of Broome North Waranyjarri Estate (Engawa, 2018).

Research indicated that ventilation was improved within Broome North. Residents also gave positive feedback in conversations about Waranyjarri Estate and the breeze they experienced in their living

Figure 17: Climate-responsive housing in the Broome North case study

spaces. This anecdotal evidence was shared amongst all but one of the volunteer residents. Many of the conversations centred around the relative coolness of their residence compared to that of their friends or their experiences in other locations around Broome (Engawa, 2018).

ENVI-met microclimatic modelling results

The ENVI-met maps below indicate conditions at the hottest time (midday) of an average summer day regarding surface temperatures, mean radiant temperature, wind speed and direction, and PET (Figure 18 to Figure 21)

Figure 18: Broome North surface temperature mapping

Figure 19: Broome North mean radiant temperature mapping

Figure 20: Broome North wind speed and direction distribution mapping

Figure 21: Broome North PET mapping

The PET results indicate that 71% of hours of the day give rise to strong heat stress and 57% extreme heat stress (Figure 22).

The ENVI-met maps indicate conditions at the hottest time of an average summer day regarding outdoor thermal comfort 3 The highest surface temperatures were in streets with dark asphalt paving (and, to a lesser degree, red asphalt paving). The coolest surface temperatures were evident in irrigated parks and under trees. Mean Radiant Temperature (MRT) was uniformly high across unshaded areas of the precinct. The wind was a typical summer sea breeze, and wind speeds were highest in the streets and parks but lowest around the leeward side of houses, particularly in backyards.

Heat stress (measured in PET thermal comfort, which includes the above factors) was generally most pronounced in private lots (~53.62°C) – particularly back and side yards – reflecting lower wind speeds, hard surfaces (both paving and walls), re-radiating heat, slightly higher humidity and in some cases, little shade from trees. Heat stress was lowest in streets and open spaces with shade from trees and where the wind was strongest (~47.21°C). The Neighbourhood Park in the southwest with minimal shade offers a modest Park Cool Island effect with PET values (~50.73°C).

3 ENVI-met projects the macro weather conditions onto the model area to produce microclimate outputs so there are some edge-effects noticable at the model boundaries.

Strong

Figure 22: Broome North Heat stress

4.2.2 Broome central

Figure 23: The Broome central case study precinct.

Case study description

The Broome central precinct case study comprises:

• Large suburban lots (~1,000m2) with generally low site building coverage and many vacant lots.

• A fine-gridded street network with a slightly intercardinal orientation (to the NNE)

• Public Open Space typically consists of a limited number of small parks.

• Single and double-storey houses (~180m2) with Colourbond roofs and various lightweight wall materials

• High tree canopy coverage of exotic and endemic trees in streets and backyards (see Figure 23)

Broome’s climate and remote location have necessitated a specific design solution, resulting in a distinctive ‘Broome’ building style (Figure 24) (Landcorp). The harsh subtropical climate, to an extent, determined the way a building was constructed, as natural cooling was the primary comfort consideration (Landcorp) Climate responses in traditional Broome architecture include:

• Deep timber-decked verandas with low eaves help provide shade protection for walls and windows.

• Permeable materials allowing for ventilation (e.g., Timber lattice, louvres, flywire and cheesecloth)

• Lightweight materials that minimise heat retention (e.g. Queen Anne corrugated iron, woodpanelled walls, and pressed metal).

• Tin shutters to shade windows

• A solar chimney to purge hot air and encourage ventilation

• Exotic and endemic tree planting to shade adjacent housing (Landcorp)

Figure 24: Traditional climate-responsive housing within the Broome case study

ENVI-met microclimatic modelling results

The ENVI-met maps below indicate conditions at the hottest time of day (midday) on an average summer day regarding surface temperatures, mean radiant temperature, wind speed and direction, and PET (Figure 25 to Figure 28).

Figure 25: Broome central surface temperature mapping

Figure 26: Broome central mean radiant temperature mapping

Figure 27: Broome central wind speed and direction distribution mapping

Figure 28: Broome central PET mapping

The ENVI-met maps indicate conditions at the hottest time of day (midday) on an average summer day, regarding outdoor thermal comfort. The results indicate that 64% of the hours of the day give rise to strong heat stress, and 36% to extreme heat stress (Figure 29).

The highest surface temperatures were modelled in streets with grey asphalt paving. The coolest surface temperatures were evident under trees on private lots. The MRT was generally uniform, except under significant trees. The wind was a typical summer sea breeze, and wind speeds were highest in the streets and private lots with low building cover. Wind speeds were lowest on the leeward side of the houses.

Heat stress (measured in PET thermal comfort) was most pronounced in backyards (~57.80°C), reflecting a lack of ventilation, and, in some cases, little shade from trees. Notably, heat stress was lowest in front yards (~40.53°C), which contained large trees, had minimal paving coverage and benefited from the breezes being funnelled down streets.

Figure 29: Broome Central heat stress

4.3 Karratha case studies

Figure 30: Karratha case studies

Climate zone

The Karratha case studies (see Figure 30) are sited within the National Construction Code designated climate zone 1: High humidity summer, warm winter (Australian Building Codes Board, 2024).

Karratha experiences a hot semi-arid climate (BSh). The region experiences warm to hot temperatures throughout the year, accompanied by generally low rainfall. Most precipitation occurs in late summer, driven by tropical cyclones and monsoonal activity, while a secondary, smaller peak can happen in early winter due to the occasional reach of southern cold fronts. Rainfall between August and December is uncommon. Winter temperatures rarely fall below 10°C, with daytime highs typically in the mid-to-high 20s, accompanied by sunny skies and low humidity. Summers are extremely hot and mostly dry, though the monsoon's unpredictable nature can sometimes bring high humidity and thunderstorms (Bureau of Meteorology, 2025).

4.3.1 Bulgarra

Case study description

Figure 31: The Bulgarra case study precinct.

The Bulgarra precinct case study comprises:

• Suburban lots (~750m2) with generally low site building coverage.

• A banded street network with an intercardinal orientation (NNW)

• Large areas of informal Public Open Space with drainage functions

• Single-storey houses (~150m2) with Colourbond steel roofs and walls.

• Reasonable tree canopy coverage in backyards and very little coverage in streets (see Figure 31)

Karratha was initially developed as a mining company town. To compensate for its isolation, the Bulgarra precinct case study was designed to loosely emulate the then-fashionable Radburn neighbourhood unit first developed in the American suburb of Radburn, New Jersey. At Radburn, vehicular and pedestrian traffic were separated using internal landscaped spines that were open space and pedestrian connections (Freestone et al., 2011). In the Pilbara region, Radburn planning principles were applied in resource towns such as Dampier (1965), South Hedland (circa 1980), and Karratha (including Bulgarra) (circa 1979). The prevalence of Radburn planning principles in the Pilbara has been identified as constituting a vital aspect of the Pilbara vernacular (Landcorp, 2012,

p. 16) Despite the prevalence of Radburn planning in the Pilbara, the results have often been disappointing, as the internal spines are functionally predominantly used as a drainage network.

Housing within the Bulgarra precinct case study exhibits modest responsiveness to climate:

• Some low eaves provide shade protection to some walls and windows

• Lightweight materials which do not store heat (e.g. Colourbond steel)

• Cardinal house orientation, which reduces heat loads on walls

• Some tree planting to shade the adjacent housing

Nonetheless, most housing appears to have been designed with a presumption that air conditioning will be used for much of the year. Streets are very poorly shaded and actively discourage walking or cycling.

ENVI-met microclimatic modelling results

The ENVI-met maps below indicate conditions at the hottest time of day (midday) on an average summer day regarding surface temperatures, mean radiant temperature, wind speed and direction, and PET (Figure 32 to Figure 35)

Figure 32: Bulgarra surface temperature mapping

Figure 33: Bulgarra mean radiant temperature mapping

Figure 34: Bulgarra wind speed and direction distribution mapping

Figure 35: Bulgarra PET mapping

The results indicate that 79% of the hours of the day give rise to strong heat stress, and 64% to extreme heat stress (Figure 36). The highest surface temperatures were modelled on asphalt roads The coolest surface temperatures were evident under trees on private lots and in the open space network. Conversely, the MRT was highest in private lots and the drainage corridor open space, and lowest in streets, reflecting that asphalt absorbs a greater proportion of short-wave radiation than bare ground. The wind was a summer sea breeze, and wind speeds were highest in the streets and on private lots with low building cover. Wind speeds were lowest on the leeward side of houses.

Heat stress (measured in PET) was most pronounced near the western face of buildings (reflecting the early afternoon sun) and in backyards (~53.94°C) (reflecting lower wind speeds), hard paving and wall surfaces re-radiating heat, and sometimes little shade from trees. Notably, heat stress was lowest in front yards (~43.00°C), which contained large trees, had minimal paving coverage and benefited from the breezes being funnelled down streets. The open space to the east appears to provide little to no Park Cool Island effect (~51.41°C).

Daylight hours

Strong heat stress 79%

Extreme heat stress 64%

Figure 36: Bulgarra heat stress

4.3.2 Karratha town centre

Case study description

Figure 37: The Karratha town centre case study.

The Karratha town centre precinct case study comprises:

• A loosely gridded street network with a cardinal orientation defined by the North-South running Sharpe Avenue

• A diversity of built forms, including Karratha City shopping centre, mid-rise apartments (Pelago East/ West Apartments), modest single-storey housing, industrial sheds,

• A substantial area of informal Public Open Space with drainage functions (in the west) and some small local open spaces.

• Minimal tree canopy coverage in either private lots or the public domain (see Figure 37)

One of the key initiatives of the state government-funded Royalties for Regions scheme was the ‘Pilbara Cities’ vision, established in 2010. The Pilbara Cities initiative aimed to build the population of Pilbara towns (such as Karratha) and simultaneously grow them into ‘more attractive, sustainable local communities’ (Pilbara Development Commission, 2016) Karratha’s town centre revitalisation aimed to create a ‘vibrant commercial heart for a population of 50,000’ (Government of Western Australia, 2010a) and included planning for:

• Medium to high-density street-fronted mixed-use redevelopment

• The realignment and traffic calming of a number of the main roads

• The creation of new parks and urban spaces

• The upgrading of drainage reserves and school grounds

• A commercial precinct (The Quarter)

• A retail precinct

• A medium to high-rise resort-style hotel

• A civic centre around existing civic buildings

• An arts precinct (The Red Earth Arts Precinct)

Previously, Karratha’s Radburn planned centre was structured by an inwardly focused shopping centre, large car parks, and a convoluted road network The result was a town centre that was drastically lacking in legibility (Watt, 2016).

Planning for climate responsiveness is generally minimal:

• Large surface car parks associated with the Karratha City shopping centre and Hearson’s Bistro absorb and reradiate heat.

• Wide roads (e.g., Karratha Terrace, Sharpe Avenue, or Warambie Road) absorb and reradiate heat, receiving slight shading from street trees or adjacent buildings.

• Generally, the precinct contains little tree canopy coverage to provide shade or evapotranspiration-related cooling. The exception is the drainage corridor, which contains numerous endemic trees.

• Most commercial or residential buildings are designed to rely on mechanical cooling to be habitable.

ENVI-met microclimatic modelling results

The ENVI-met maps below indicate conditions at the hottest time (midday) of an average summer day regarding surface temperatures, mean radiant temperature, wind speed and direction, and PET (Figure 38 to Figure 41).

Figure 38: Karratha town centre surface temperature mapping

Figure 39: Karratha town centre mean radiant temperature mapping

Figure 40: Karratha town centre wind speed and direction distribution mapping

Figure 41: Karratha town centre PET mapping

The results indicate that 71% of hours of the day give rise to strong heat stress and 64% to extreme heat stress (Figure 42). Levels of heat stress are slightly lower in Karratha Town Centre compared to Bulgarra due to some shading from buildings and mature trees.

The highest surface temperatures were modelled in streets and carparks adjacent to buildings, due to re-radiating heat from walls, and to a lesser extent, in streets and carparks with grey asphalt paving. The coolest surface temperatures were evident in irrigated open spaces and the central courtyards of some buildings. MRT was highest in private lots and open spaces (including the drainage corridor). MRT was lowest in areas shaded by built form. The wind was a typical summer sea breeze, and wind speeds were highest in the streets (particularly those running northwest to southeast) and lowest on the leeward side of major multi-story buildings.

Heat stress (measured in PET) was most pronounced in areas immediately adjacent to built form (~60.27°C) due to hard paving and wall surfaces re-radiating heat, as well as in some cases, lower wind speeds and limited shade from trees. The exception was that heat stress was lowest adjacent to the east faces of the built form, due to the afternoon shade provided by buildings (~38.77°C).

Irrigated green spaces with few trees and the drainage corridor provided little or no Park Cool Island effect (~52.17°C).

Figure 42: Karratha Town Centre heat stress

4.4 Results: Geraldton case study

Figure 43: Geraldton case study

Climate zone

The Geraldton case study (see Figure 43) is situated within the National Construction Code's designated climate zone 5: Warm Temperate (Australian Building Codes Board, 2024) Geraldton features a Mediterranean climate (Csa) with some semi-arid (Bsk) characteristics. Summers are extended and hot, though nights remain relatively mild. Winters are brief, mild, and wetter, with cooler nighttime temperatures. In winter, daytime temperatures hover around 20°C, and this season accounts for most of the annual rainfall. Summer highs typically range between 32 °C and 33°C, with occasional days exceeding 40°C. Coastal areas benefit from cooling afternoon sea breezes (Bureau of Meteorology, 2025)

4.4.1 Maitland Park

Case study description

Figure 44: The Maitland Park case study precinct.

The Maitland Park precinct case study comprises:

• A triangular District Park (Maitland Park) with extensive turf and minimal tree planting

• Several schools, including Geraldton Senior High School, St Francis Xavier Primary School, Geraldton Primary School and Nagle Catholic College

• A small pocket of suburban lots (~1,000m2) with generally low site building coverage.

• A triangular network of roads (several of them arterial)

• Generally, streets have low tree canopy coverage (Figure 44)

Maitland Park’s function and use are primarily influenced by its proximity to five major schools, the precinct forming a green connection between them (UDLA, 2023) Identified as a District Park in the 'City of Greater Geraldton Public Open Space Strategy', Maitland Park is an ample public open space (POS) that is valued by the community for its:

• Existing established trees, undulating turf space and amenities

• Parking opportunities for the surrounding schools

• Positioning on Cathedral Avenue as an 'Entry Statement' into town (UDLA, 2023)

A concept master plan has been prepared to upgrade the park. This master plan includes proposals for:

• A transport hub/ bus port

• A multi-use community/school pavilion

• A youth plaza

• A nature playground

• Outdoor learning spaces.

The diversity of built form and open space in the precinct showcases different levels of climate responsiveness. However, climate responsiveness is generally minimal:

• While comprising substantial open space areas, tree canopy cover is low, reducing shade or evapotranspiration-related cooling.

• Wide roads (e.g., Cathedral Avenue) absorb and reradiate heat and receive slight shading from street trees or adjacent buildings.

• Poor intercardinal building orientation within schools

Nonetheless, the concept masterplan proposes more trees and shade within the park, featuring a 'mid-west arboretum' design that showcases and celebrates the unique tree species of the region. It is proposed that rows of newly planted trees will provide a healthy canopy of shade, accentuate species diversity, and enhance sightlines (UDLA, 2023)

ENVI-met microclimatic modelling results

The ENVI-met maps below indicate conditions at the hottest time of day (midday) on an average summer day regarding surface temperatures, mean radiant temperature, wind speed and direction, and PET (Figure 45 to Figure 48)

Figure 45: Maitland Park surface temperature mapping

Figure 46: Maitland Park mean radiant temperature mapping

Figure 47: Maitland Park wind speed and direction distribution mapping

The results indicate that 50% of the hours of the day result in strong heat stress, and 7% in extreme heat stress (Figure 49). The highest surface temperatures were modelled in paved areas immediately to the north of buildings (due to facades reradiating long-wave radiation) and streets with asphalt paving. The coolest surface temperatures were evident in irrigated green spaces. MRT was highest adjacent to exposed north-facing building facades. MRT was lowest in areas shaded by built form. The wind was a typical summer sea breeze, and wind speeds were highest in the park and lowest on the leeward side of the school buildings. Heat stress is most pronounced around school buildings, which impede ventilation and radiate heat (~54.09°C). The park area itself is the coolest part of the precinct, indicating the presence of a modest Park Cool Island effect (~38.54°C).

Figure 48: Maitland Park PET mapping

4.5 Results: Toodyay case study

Figure 50: The Toodyay case study, River Hills Estate.

Climate zone

The Toodyay case study is situated within the National Construction Code's designated climate zone 5: Warm Temperate (Australian Building Codes Board, 2024) (Figure 50). Toodyay has a hot-summer Mediterranean climate (Köppen: Csa), characterised by hot, dry summers and mild, rainy winters (Bureau of Meteorology, 2025).

Figure 49 Maitland Park heat stress

4.5.1

River Hills Estate

Case study description

Figure 51: The River Hills Estate case study precinct.

The River Hills Estate precinct case study comprises:

• Large suburban lots (~1,000m2) with generally moderate site building coverage.

• An organic street network with an intercardinal orientation

• Large single-storey houses (~250m2) with Colourbond steel roofs.

• Stands of retained endemic trees in backyards.

• The estate lacks Public Open Space but is adjacent to the Avon River reserve (see Figure 51)

Founded in the 1870s, Toodyay features a gridded street system, and its urban fabric consists of lowdensity, free-standing houses with historic one- to two-storey architecture, containing commercial and civic functions concentrated on a central main street The Toodyay River Hills Estate is a comparatively new expansion to Toodyay’s traditional urban form.

Housing within the River Hills Estate precinct case study exhibits only modest responsiveness to climate:

• General setbacks to the northern edges of lots to allow winter sun

• Some eaves and verandas provide shade protection to the walls

• Some window hoods provide shade protection to windows

• Some light-coloured ‘cool roofs’ to reflect heat

• There is some retention of trees in backyards, but minimal canopy coverage in streets.

• Poor house orientation due to intercardinal lot arrangements often increases heat loads on walls.

ENVI-met microclimatic modelling results

The ENVI-met maps below indicate conditions at the hottest time (midday) of an average summer day regarding surface temperatures, mean radiant temperature, wind speed and direction, and outdoor thermal comfort (Figure 52 to Figure 55).

Figure 52: River Hills Estate surface temperature mapping

Figure 53: River Hills Estate mean radiant temperature mapping

Figure 54: River Hills Estate wind speed and direction distribution mapping

Figure 55: River Hills Estate thermal comfort mapping

The results indicate that 71% of hours of the day give rise to strong heat stress and 57% to extreme heat stress (Figure 56). The highest surface temperatures were modelled in streets and, to a lesser degree, in sparse bushland and wheatfields. The coolest surface temperatures were evident under stands of trees and on the shaded south sides of buildings. MRT was highest in private lots and open spaces and lowest in areas shaded by trees and built form. The wind was a south-easterly land breeze, and wind speeds were generally consistent across the case study due to the large distances between houses. Heat stress varied little across the case study (~2.93°C), although some cooling is associated with protection from shade and trees (~42.19°C)

4.6 Results: Perth case studies

4.6.1 Climate zone

The Perth case studies (see Figure 57) are located within the National Construction Code's designated climate zone 5: Warm Temperate (Australian Building Codes Board, 2024). Perth experiences a Mediterranean climate (Köppen classification Csa), characterised by hot, dry summers and mild, wet winters. February is typically the hottest month, with an average high of 31.6°C, while July is the coldest, with an average low of 7.9 °C. Approximately 77% of the city’s annual rainfall occurs between May and September (Bureau of Meteorology, 2025).

Figure 56 River Hills Estate heat stress

Figure 57 Perth region case studies

4.6.2

Jindalee

Case study description

The Jindalee precinct case study comprises:

• Compact suburban lots (~350-500m2) with high-site building coverage.

• A fine-gridded street network with a cardinal orientation

• Public Open Space typically consists of small Local or Neighbourhood parks.

• Generally single-storey houses (~250m2) with Colourbond steel roofs.

• Minimal tree canopy coverage in streets and backyards (see Figure 58)

The precinct case study reflects the prevailing Liveable Neighbourhoods design code, which has the following aims:

• To provide for an urban structure of walkable neighbourhoods clustering to form towns of compatible mixed uses to reduce car dependence for access to employment, retail and community facilities (West Australian Planning Commission & Department of Planning, 2009)

• To provide access generally through an interconnected network of streets that facilitate safe, efficient, and pleasant walking, cycling, and driving (West Australian Planning Commission & Department of Planning, 2009).

• Greater lot size variety for housing choice and affordability, and the establishment of higher densities (West Australian Planning Commission & Department of Planning, 2009).

Figure 58 The Jindalee case study precinct.

The Liveable Neighbourhoods policy calls for basic climate responsiveness:

• Predominantly north-south or east-west street orientation to enable lot layout for solar access.

• Appropriate building setbacks from the northern property boundary to enable good winter sun access to suitably located and sized windows.

• Street verges of sufficient width to accommodate all anticipated services, including adequate space for large canopy street trees of an appropriate species for shade provision (West Australian Planning Commission & Department of Planning, 2009)

Despite aspirations in Liveable Neighbourhoods, the Jindalee precinct case study reflects minimal responsiveness to climate:

• Poor solar orientation of houses despite the cardinal grid and east-west running lots

• Minimal setback of houses from the northern edge to allow access to winter sun (Figure 59)

• Minimal canopy cover to provide shade and evapotranspiration-related cooling, noting that some trees are still juvenile

• Small neighbourhood parks that trade off size for accessibility but yield slight urban cooling

ENVI-met microclimatic modelling results

The ENVI-met maps below indicate conditions at the hottest time (midday) of an average summer day regarding surface temperatures, mean radiant temperature, wind speed and direction, and outdoor thermal comfort (Figure 60 to Figure 63).

Figure 59 The Jindalee case study area.

Figure 60: Jindalee surface temperature mapping

Figure 61: Jindalee mean radiant temperature mapping

Figure 62: Jindalee wind speed and direction mapping

Figure 63: Jindalee PET mapping

The results indicate that 43% of the hours give rise to strong heat stress and 21% extreme heat stress (around midday)(Figure 64). Surface temperatures were highest in streets, particularly those running east-west and lowest in open spaces and under significant trees. MRT was highest in private lots and open spaces. MRT was lowest in areas shaded by built form. The wind was a typical southsouthwesterly sea breeze, and wind speeds were highest in the streets running north-south and lowest on the leeward side of houses and east-west running streets Heat stress (measured in PET) was most pronounced in private lots (~58.06°C), particularly in back and side yards, reflecting lower wind speeds, hard surfaces (both paving and walls), re-radiation of heat, and generally little shade from trees. Heat stress was high in streets and parks running east-west (~47.44°C) and lowest in northsouth streets (~43.16°C) where the wind was strongest. The central neighbourhood park offered no Park Cool Island effect, with heat stress more pronounced (~46.04°C) than on the north-south running streets.

Figure 64 Jindalee heat stress

4.6.3

Nollamara

Case study description

Figure 65 The Nollamara case study precinct.

The Nollamara precinct case study comprises:

• Unsubdivided suburban lots (~750m2) with generally low site building coverage.

• Survey strata lots (~250m2) with high site building coverage

• A gridded street network, which is both cardinal and intercardinal

• A small Local Public Open Space

• One to two-storey houses (~150 - 250m2)

• High tree canopy coverage in unsubdivided lots, moderate coverage in streets and minimal coverage in subdivided lots.

The Nollamara precinct is an example of ‘background’ infill, which comprises a small-scale, single or double-storey, semi-detached survey strata and typically two to seven group dwellings organised around a shared driveway (Bolleter, 2016) Background infill typically occurs when suburbs are rezoned to facilitate subdivision and development.

Housing within the Nollamara precinct case study exhibits modest responsiveness to climate:

• Small eaves provide minimal shade protection to some walls and windows.

• Intercardinal house orientation, which increases heat loads on walls.

• A lack of tree planting to provide shade for pedestrians or adjacent housing.

• Dark roofs and paving absorb and re-radiate heat.

ENVI-met microclimatic modelling results

The ENVI-met maps below indicate conditions at the hottest time (midday) of an average summer day regarding surface temperatures, mean radiant temperature, wind speed and direction, and PET (Figure 66 to Figure 69)

Figure 66: Nollamara surface temperatures mapping

Figure 67: Nollamara mean radiant temperature mapping

Figure 68: Nollamara wind speed and direction mapping

Figure 69: Nollamara thermal comfort mapping

The results indicate that 54% of the day's hours give rise to strong heat stress, and 46% to extreme heat stress (Figure 70).

The highest surface temperatures were modelled in streets and driveways. The coolest surface temperatures were evident in open spaces and unsubdivided backyards. MRT was highest in private lots due to a lack of tree canopy and the reradiation of heat from walls and paved surfaces. MRT was lowest in areas shaded by significant trees. The wind was a typical south-westerly sea breeze, and wind speeds were highest in the streets running generally east-west. Windspeeds were lowest around tightly clustered infill housing.

Heat stress (measured in PET) was most pronounced in private lots (~53.78°C), particularly in back and side yards, reflecting lower wind speeds, hard surfaces (both paving and walls), re-radiation of heat, and generally little shade from trees. Heat stress was less pronounced in east-west running streets (~52.86°C) with the strongest wind, and street trees provided shade. Again, the Neighbourhood Park offered little cooling effect (~53.11°C)

Strong

Extreme

4.6.4

Case study description

The Leederville town centre case study comprises:

Figure 70 Nollamara heat stress

Leederville town centre

Figure 71: The Leederville case study precinct.

• Historic high streets along Oxford and Newcastle streets

• Low-rise mixed-use buildings along high streets and some emerging medium-rise apartment buildings

• Large public buildings (e.g. the Water Corporation headquarters)

• A train station within the adjacent freeway reserve

• Significant surface-level car parks for transit users to park and ride.

• Moderate tree canopy coverage in streets and communal open space (Figure 71).

The broader Leederville town centre is a designated ‘Secondary Centre’ under the State Government's Activity Centres policy and is a significant Transit-Oriented Development along the Joondalup rail line (Government of Western Australia, 2010b, p. 4140). Activity centres are community focal points that feature a mix of land uses, including offices, civic, business, health, community, and entertainment/cultural uses (Government of Western Australia, 2010b, p. 4147) The Leederville town centre precinct is now part of the Leederville Precinct Structure Plan (LPSP) area, guiding future development (City of Vincent, 2021) The LPSP proposes to increase density near the train station, allowing for transport choice, and will deliver 1,528 new dwellings at a residential site density of 60 dwellings per hectare, as well as expanding the centre’s offering of a wide variety of land uses (City of Vincent, 2021).

The LPSP advocates for the following climate-responsive design principles:

• Ensuring slender, well-spaced towers and appropriate podium treatments that maximise solar access to adjoining buildings and public spaces (City of Vincent, 2021).

• Ensuring that all new buildings are oriented to optimise solar access, natural cross-ventilation, and the incorporation of thermally efficient building materials (City of Vincent, 2021).

• Increasing landscaping and tree canopy cover within the public realm is the priority, followed by appropriate landscaping on private land (City of Vincent, 2021).

ENVI-met microclimatic modelling results

The ENVI-met maps below indicate conditions at the hottest time (midday) of an average summer day regarding surface temperatures, mean radiant temperature, wind speed and direction, and PET (Figure 72 to Figure 75).

Figure 72: Leederville town centre surface temperature mapping

Figure 73: Leederville town centre mean radiant temperature mapping

Figure 74: Leederville town centre wind speed and direction mapping

Figure 75: Leederville town centre thermal comfort mapping

The results indicate that 64% of hours of the day give rise to strong heat stress and 43% extreme heat stress (Figure 76). The highest surface temperatures were modelled in streets and carparks adjacent to buildings due to re-radiating heat from walls. The coolest surface temperatures were evident in the central courtyards of some buildings and under substantial street trees. The MRT was highest in private lots, and the lowest MRT was under trees, generally in streets. The wind was a typical southwesterly sea breeze, and wind speeds were highest in open areas and lowest on the leeward side of clusters of buildings. Heat stress (measured in PET) was pronounced across the precinct, particularly adjacent to closely packed buildings and courtyards (~58.76°C), due to lower wind speeds, hard paving, and wall surfaces re-radiating heat, as well as, in some cases, little shade from trees. Notably, less heat stress was felt under major trees in the streets and carparks (~44.56°C)

Daylight hours Strong

Figure 76 Leederville Town Centre heat stress

4.6.5

Central Perth

Case study description

Figure 77: The central Perth case study precinct.

The central Perth case study comprises:

• High-rise apartment buildings along Adelaide Terrace step down to low- and mid-rise apartments along Hay Street.

• A gridded street network, which is slightly intercardinal (oriented to the NNE)

• Moderate tree canopy coverage in streets and low canopy cover in private or communal open spaces (Figure 77).

The broader Perth city centre is designated as a ‘Capital City’ under the State Government Activity Centres policy (Government of Western Australia, 2010b). Activity centres are community focal points that feature a mix of land uses, including offices, civic, business, health, community, and entertainment/cultural uses (Government of Western Australia, 2010b). The Central Perth case study is part of the City of Perth, City Planning Scheme No 2 ‘Adelaide Precinct’ (City of Perth, 2024). The scheme proposes that the precinct will be continue to function as a residential quarter, accommodating a wide range of residential, visitor accommodation, and employment opportunities (City of Perth, 2024)

The scheme advocates for the following climate-responsive design principles:

• A grand-scale boulevard planting along Adelaide Terrace and Plain Street to provide shade

• An appropriate level of sunlight penetration into key pedestrian and public spaces

• Minimisation of adverse wind impacts (City of Perth, 2024).

ENVI-met microclimatic modelling results

The ENVI-met maps below indicate conditions at the hottest time (midday) of an average summer day regarding surface temperatures, mean radiant temperature, wind speed and direction, and outdoor thermal comfort (Figure 78 to Figure 81).

Figure 78: Central Perth surface temperature mapping

Figure 79: Central Perth mean radiant temperature mapping

Figure 80: Central Perth wind speed and direction mapping

Figure 81: Central Perth thermal comfort mapping

The results indicate that 57% of the day's hours give rise to strong heat stress and 50% to extreme heat stress (Figure 82). The highest surface temperatures were modelled in streets and carparks adjacent to buildings due to re-radiating heat from walls. The coolest surface temperatures were evident in areas shaded by buildings and trees. MRT was highest in exposed areas to the north of buildings and lowest in shaded areas to the south of the built form. The wind was a comparatively south-west sea breeze, and wind speeds were highest in the streets and lowest on the leeward side of major multistorey buildings. Levels of heat stress were lowest in shaded areas to the south of buildings and under mature trees (~45.09°C) Levels of heat stress were highest in areas with poor ventilation, which are exposed to short- and long-wave radiation (~57.32°C)

Daylight hours

Extreme heat stress 50%

Figure 82 Perth Central heat stress

4.6.6 Karawara

Case study description

Figure 83: The Karawara case study precinct.

The Karawara precinct case study comprises:

• Suburban lots (~750m2) with generally low site building coverage.

• A disconnected street network of cul-de-sacs running generally north-south

• Spines of Public Open Spaces running between lines of houses

• One to two-storey houses (~200m2)

• High tree canopy coverage in backyards and, to a lesser extent, streets (see Figure 83)

The Karawara precinct reflects 1970s-era Radburn planning. The Radburn neighbourhood unit was first developed in the American suburb of Radburn, New Jersey. Radburn's planning separated

vehicular and pedestrian traffic using internal landscaped spines with open spaces and pedestrian routes (Freestone et al., 2011)

Housing within the Karawara precinct case study exhibits modest responsiveness to climate:

• Small eaves provide minimal shade protection to some walls and windows

• Intercardinal house orientation, which increases heat loads on walls

• Significant tree planting to shade adjacent housing.

ENVI-met microclimatic modelling results

The ENVI-met maps below indicate conditions at the hottest time (midday) of an average summer day regarding surface temperatures, mean radiant temperature, wind speed and direction, and outdoor thermal comfort (Figure 84 to Figure 87).

Figure 84: Karawara surface temperature mapping

Figure 85: Karawara mean radiant temperature mapping

Figure 86: Karawara wind speed and direction mapping

The results indicate that 57% of hours of the day give rise to strong heat stress and 50% extreme heat stress (Figure 88). The highest surface temperatures were modelled in streets. The coolest surface temperatures were evident in open spaces, particularly under trees. MRT was highest in private lots and open spaces, except under significant trees. The wind was a typical summer sea breeze, with wind speeds highest in the streets and open spaces, and lowest on the leeward side of the housing. Heat stress is relatively consistent across the case study, and surprisingly, the POS spines offered little cooling (~54.31°C) other than under large trees (~47.82°C).

Figure 87: Karawara thermal comfort mapping

4.6.7 Cockburn Central

Case study description

Figure 89: The Cockburn central case study precinct.

The Cockburn Central Precinct case study comprises:

• Emerging medium-rise perimeter block apartment buildings are generally 3-5 storeys (see Figure 89).

• A fine-gridded street network with generally cardinal orientation.

• A train station within the adjacent freeway reserve

• Significant surface-level car parks for transit users to park and ride.

• A small urban public space adjacent to a train station.

• Communal courtyards, comprising either landscape or car parks, are defined by perimeter block buildings.

• Low but emerging tree canopy coverage in streets and communal open space

The broader Cockburn Central development is a designated ‘Secondary Centre’ under the State Government's Activity Centres policy and is a significant Transit-Oriented Development along the Mandurah rail line (Government of Western Australia, 2010b, p. 4140). Activity Centres are community focal points (Government of Western Australia, 2010b, p. 4140), and Cockburn Central is intended to provide opportunities for retail, office, commercial and residential activity to ‘achieve a vibrant and active destination’ (Landcorp, 2016) While the precinct is still in development, it is

Figure 88 Karawarra heat stress

anticipated that the predominant development form will be medium- to high-density residential dwellings. However, ground-floor non-residential land use is mandated at key locations and encouraged in other supporting locations (Landcorp, 2016).

The design guidelines for the adjacent Cockburn Central West precinct include several provisions for climate-responsive design (Landcorp, 2016) These include:

• Ensure the apartment design allows for effective use of night ventilation and air purging to help maintain comfortable internal temperatures

• Ensure that the built form is conceived to allow good solar access to the public realm and adjacent buildings whilst achieving comfortable internal and external environments for its occupants.

• Incorporate passive solar design principles to optimise winter solar gain and protection from summer heat gain.

• Ensure that at least 70% of dwellings in multi-residential developments have outdoor areas that benefit from a northerly aspect.

• Maximise natural ventilation potential by orienting buildings and their openings to maximise air intake from the ‘windward’ side of the building and by providing air outlets on the ‘leeward’ side

• Design residential dwellings to maximise cross ventilation by providing direct breeze paths for cooling and air circulation (Landcorp, 2016)

ENVI-met microclimatic modelling results

The ENVI-met maps below indicate conditions at the hottest time (midday) of an average summer day regarding surface temperatures, mean radiant temperature, wind speed and direction, and PET (Figure 90 to Figure 93)

Figure 90: Cockburn Central surface temperature mapping

Figure 91: Cockburn Central mean radiant temperature mapping

Figure 92: Cockburn Central wind speed and direction mapping

Figure 93: Cockburn Central PET mapping

The results indicate that 36% of the day's hours give rise to strong heat stress and 29% to extreme heat stress (Figure 94). The highest surface temperatures were modelled in streets and carparks adjacent to buildings due to re-radiating heat from walls. The coolest surface temperatures were evident in the central courtyards of some buildings and under substantial street trees. The MRT was highest on private lots and undeveloped areas, relative to streets, where bare soil reflects high levels of short-wave radiation The lowest MRT was typically found under significant trees, often in streets. The wind was a westerly summer sea breeze, and wind speeds were highest in the east-west running streets and lowest in the courtyards of apartment buildings.

Heat stress (measured in PET) was pronounced on the north and east sides of multi-storey buildings (~57.64°C), and in some hard landscaped courtyards, due to generally lower wind speeds, little shade from trees, and hard paving and wall surfaces re-radiating heat. Heat stress was also pronounced in many vacant sites. Notably, heat stress was least pronounced under major trees in streets and landscaped courtyards (~35.79°C).

Figure 94: Cockburn Central heat stress

Case study description

The Salt Lane precinct case study comprises:

• Compact lots (~130- 200m2) with generally high site building coverage.

• A gridded street network with both cardinal and intercardinal orientation

• A central spine of Public Open Space with some drainage function

• One to two-storey terrace housing with planned low-rise perimeter block apartments

• There is minimal tree canopy coverage on private lots, and significant canopy cover is found in parks and, to a lesser extent, on streets (See Figure 95).

ENVI-met microclimatic modelling results

The ENVI-met maps below indicate conditions at the hottest time (midday) of an average summer day regarding surface temperatures, mean radiant temperature, wind speed and direction, and PET (Figure 96 to Figure 99).

4.6.8 Salt Lane

Figure 95: The Salt Lane case study precinct.

Figure 96: Salt Lane surface temperature mapping

Figure 97: Salt Lane mean radiant temperature mapping

Figure 98: Salt Lane wind speed and direction mapping

Figure 99: Salt Lane PET mapping

The results indicate that 50% of the hours of the day are associated with strong heat stress, and 43% exhibit extreme heat stress (Figure 100). The highest surface temperatures were modelled in streets, and the coolest were evident in irrigated open spaces. MRT was highest in private lots adjacent to exposed building faces and in areas with light coloured ground surfaces. MRT was lowest in areas shaded by built form and under substantial trees. The wind was a westerly sea breeze, and wind speeds were highest in streets and open spaces and lowest on the leeward side of buildings. Heat stress (measured in PET) was most pronounced in undeveloped lots and adjacent to sun-exposed building faces (~52.07°C). Heat stress was lowest under mature trees and along the south faces of buildings (~38.79°C)

Figure 100 ENVI-met results – Salt Lane

5. Discussion

5.1 Our findings and the

literature

Below, we consider some key findings from our modelling.

5.1.1 Marginal Park Cool Island effects

Numerous studies have demonstrated the cooling effect of vegetation (and particularly trees) on their surroundings. These effects are referred to as Park Cool Islands (PCIs) but can also be applied to vegetation in streets and private lots (Lenzholzer, 2015, p. 72; Rakoto et al., 2021). The cooling effect occurs because vegetation intercepts most of the sun’s energy, reflecting some and absorbing some for photosynthesis, reducing the amount of heat absorbed and providing shade (Lenzholzer, 2015) Secondly, evaporation from vegetation is also a factor in lowering the air temperature (Lenzholzer, 2015). The conversion of liquid to gas utilises heat, which reduces the temperature of the air and the tree/soil that stores that heat (Cooperative Research Centre for Water Sensitive Cities, 2020).

Studies have assessed the PCI effect by analysing the PCI intensity, reflecting the temperature differential between the park and surrounding urban areas (García-Haro et al., 2023). The calculated values for this indicator have shown a wide range, varying from 0.1°C to 6.9°C, with an average temperature drop ranging between 0.30°C and 1.90°C (García-Haro et al., 2023). The PCI extent, also known as Park Cooling Distance (PCD), refers to the maximum distance over which the cooling effect spreads beyond the park's boundaries (García-Haro et al., 2023). Studies on the spatial extent of the PCI have yielded an average of 100 meters, with a range of 10 to 440 meters (García-Haro et al., 2023).

Surprisingly, the parks in our case study areas provided little cooling (as assessed through PET), and certainly, no cooling effects extended any significant distance outside of the park itself (PCD). This situation occurs because most of the parks in our case study areas had minimal tree canopy cover, which provides shade and, to a lesser extent, evaporative cooling (Figure 101). Indeed, studies have found that the greatest PCI intensity relies on extensive tree canopy cover to block out penetrating

solar radiation and, at the same time, offer evaporative cooling (Brown et al., 2015; García-Haro et al., 2023; Vanos et al., 2012)

Figure 101: The lack of tree canopy cover in parks (Karratha town centre pictured) means the parks cannot provide a meaningful PCI effect.

5.1.2 Differences between LST and PET

A counter-intuitive finding was the difference between LST and PET values in our case study areas. Take, for instance, our Broome North case study (Figure 102); LST modelling shows roads to be significantly hotter than parks, as would be expected (Algretawee et al., 2019). However, surprisingly, the PET values indicate that thermal comfort is lower in the middle of many streets than in parks, even when both locations are in full sun. This situation is likely occurring due to several reasons. Firstly, many streets are better ventilated than parks; moreover, the asphalt surface absorbs and stores more short-wave radiation and reflects less long-wave radiation onto a person standing at ~1.8m high. These results should caution researchers from correlating surface temperatures with thermal comfort, as found in several studies (For example Algretawee, 2022) – as our modelling shows that the two are substantially different and that LST values have little significance in relation to human thermal comfort (as assessed through PET).

Figure 102: While a Broome North park registers as significantly cooler in terms of LST, the park (on the left of the image) has surprisingly high PET values, indicating little correlation between LST and PET.

5.2 Implications for urban planning and design policy

5.2.1 The problems of compact suburbs

In almost all our case studies, thermal discomfort is most extreme in areas adjacent to clustered housing, as exemplified in the background infill in the Nollamara case study or compact suburbs in Jindalee (Figure 103). This situation primarily reflects lower wind speeds and, to a lesser extent, hard surfaces (both paving and walls), which re-radiate heat and, in some cases, provide little shade from trees. In particular, greater attention is warranted to the arrangement and spacing of housing to facilitate ventilation while still increasing overall urban density.

Figure 103: Heat stress was often highest adjacent to built form. The compact suburban layout of the Jindalee case study is pictured

State Planning Policy 7.1 Neighbourhood Design calls for basic climate responsiveness with predominantly north-south or east-west street orientation to enable lot layout for solar access; appropriate building setbacks from the northern property boundary to enable good winter sun access; and street verges of sufficient width for large canopy street trees of an appropriate species for shade provision (West Australian Planning Commission & Department of Planning, 2009). It is less clear how these compact suburban arrangements ensure adequate ventilation to improve thermal comfort (e.g. Jindalee). While broadly conforming to State Planning Policy 7.1 Neighbourhood Design, Broome North has been designed with breezeways on the south or east side of lots and smaller dwelling footprints to provide breezeways between houses (Landcorp, 2011) Our modelling reveals that these initiatives have enabled modest ventilation around houses (Figure 104).

Figure 104: Broome North wind modelling reveals modest ventilation around houses

5.2.2

Ensuring urban canopy cover

The lack of canopy cover in private lots, parks and streets was a factor in the levels of heat stress in our case study precincts (Figure 105). The need to increase tree canopy cover in the precinct case studies is well understood by the respective local governments, most of whom have operational urban forest policies. Nonetheless, there are many barriers to increasing canopy cover. In the compact suburb and background infill case studies (e.g. Jindalee and Nollamara), the combination of small lots and large houses means that backyards are too small to accommodate signficant tree planting. In the TOD precincts (e.g., Leederville town centre), trees compete with underground power lines, car parking, and underground services on the verges.

Figure 105: A lack of tree canopy cover in the Nollamara case study is reflected in MRT values

In the Kimberley and Pilbara case studies (e.g., Bulgarra), naturally occurring trees are small with sparse canopies due to climate impacts (e.g., cyclonic winds), and as such, provide limited shade. Meanwhile, water shortages – particularly in Perth – limit the amount of irrigation water for newly established trees. Finally, at the state level, there is no statutory protection for trees on private lots –although we note the DPLH is preparing a Perth and Peel Urban Greening Strategy (Department of Planning Lands and Heritage, 2025). Fostering healthy and extensive urban forests will require reprioritising trees in the urban environment, appropriate funding for tree planting efforts, and statutory protection for tree specimens on privately owned land.

5.2.3

Climate assessments of urban development

Given the urgency and importance of urban adaptation to extreme heat, future reviews of the policies – State Planning Policy (SPP) 7.1 Neighbourhood Design, SPP 7.3 Residential Design CodesVolumes 1 and 2), SPP 7.2 Precinct Design and SPP 4.2 Activity Centres should mandate Climate Sensitive Urban Design (CSUD) features (Lenzholzer, 2015). These could include orienting and widening streets to the prevailing wind direction (Oke et al., 2017), designing parks with significant tree canopy cover to maximise PCI effects (Lenzholzer, 2015, p. 72), breezeways to allow ventilation (Kusumastuty et al., 2018), providing a diversity of microclimates (Oke et al., 2017), using high albedo materials (where appropriate) (Nardino & Laruccia, 2019), employing passive irrigation to maximise evaporative cooling (Cooperative Research Centre for Water Sensitive Cities, 2020), shading street

sections with buildings or trees (Oke et al., 2017), providing breezeways on private lots (Landcorp, 2014) and orienting built form to avoid solar gain on buildings (Oke et al., 2017) – amongst others. Beyond including appropriate CSUD features, development proponents should also be required to conduct a climate analysis of proposed urban development patterns to understand the degree to which they will expose resident populations to strong/ extreme heat stress – either in outdoor environments or in dwellings. While intersections between urban form and solar access are generally well understood, such modelling should include a particular focus on natural ventilation, as this has been currently overlooked in the policy frameworks – and our modelling reveals its importance for thermal comfort.

5.3 Challenges ahead

Collectively, our findings suggest that significant challenges lie ahead. The prevalence of strong to extreme heat stress in all the case studies indicates the need to fundamentally reimagine urban precincts for climate comfort now and in the future, given climate change projections of worsening summer conditions (Australian Academy of Science, 2021). Indeed, our results indicate that there is a low threshold for dealing with projected increases in temperatures in our urban environments (Australian Academy of Science, 2021)

The nexus of increasing temperatures and water scarcity in the southern case studies presents a particularly difficult challenge in providing urban forests that deliver urban cooling while not exacerbating water shortages (Australian Academy of Science, 2021). How planners and designers reconcile increasing urban densities with delivering urban cooling will also remain a significant challenge. For instance, while the Broome Central case study may deliver more thermal comfort in outdoor environments, it does so at a significantly lower density than Broome North. Moreover, the lower socio-economic status of some of the case studies most affected by heat stress (e.g. Bulgarra) raises questions about the ability of residents to actively adapt to climate change (rather than just attempting to cope).

6. Conclusions

According to the IPCC, Australia’s current reactive climate ‘adaptation’ is insufficient, too late, too little, and too costly (IPCC, 2022). Indeed, our analysis has shown that strong to extreme heat stress is evident in all case studies in the middle part of the day. Regardless, Australia is still ‘flying almost blind’ regarding adaptation to the current climate (Flannery, 2020) – let alone future climate conditions - and many planning decisions proceed on a business-as-usual basis (Flannery, 2016). This situation is concerning because the 'built environment' is a heavy, fixed thing, slow and expensive to change (Gleeson, 2006). The adaptation task is ‘vast, almost unquantifiable, but the quicker we confront it, the better we can manage’(O'Neil & Watts, 2015)

Planners and designers must prepare communities for a future climate. However, our analysis reveals that the current and historic planning for the case study neighbourhoods has resulted in environments that yield strong to extreme heat stress in average summer conditions. Why is this? Unfortunately, most actors involved in the planning and design process are busy sorting through the immediate issues they face, and planning for long-term climate change can be ‘too hard; thus, we go on with business as usual’ (Seamer, 2019) If we are to take mitigating heat stress seriously – as we should - this will require us to fundamentally reimagine urban precincts in the future.

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