Guide to Climate-Smart Playgrounds: Research Findings and Application

Outdoor play is vital for positive socialisation and development of children including cognitive, psychological, and physiological benefits. Playing outdoors increases attention, creative thought processes and problem-solving skills as well as combating obesity, mental health problems and improving social skills of children. Encouraging and supporting outdoor play is particularly important today, where the daily time interval children are engaging in physical activity is contracting. However, the lack of shade and hot playground equipment make it unsafe for children to enjoy playgrounds in summer. This situation is particularly problematic in times where summer heat is increasing as result of climate change, which already limits the time for safe outdoor play. Now more than ever is it necessary to start building climate-smart playgrounds. This report has two parts. Part 1 establishes the facts around heat in playgrounds. We document surface, air and feels like temperatures in public playgrounds across the Cumberland Local Government Area. All playgrounds were visited repeatedly during warm and hot conditions in the summer of 2019/20 and 2020/21. Part 1 also provides systematic analyses of surface temperatures of SBR, EPDM, TPO, synthetic turf and real grass. In Part 2 we describe the process, outputs and outcomes of a playground transformation at Memorial Park in Merrylands. The playground is in the Local Government Area of Cumberland City Council in the geographic centre of Sydney. With support from the NSW Government, Cumberland City Council, industry partners and inputs from a range of stakeholders, we created Australia’s first dedicated UV-smart Cool Playground. Since October 2020, the playground is enjoyed by the local community. Research data showing the avoided heat, improved thermal comfort and reduced exposure to UV-A and UV-B are provided and demonstrate the functionality of the playground

Cool Roads Trial 2021

Intensifying summer heat and associated Urban Heat Island Effects are a risk to public and environmental health. They contribute to higher energy consumption and associated greenhouse gas emissions in cities. Across Greater Western Sydney, home of the fastest growing urban population in Australia, increasing heat is recognised as the largest risk to local populations and economies. A range of interventions across the region aim at mitigating the negative impacts of heat. The Cool Roads Trial is one of these interventions. It addresses the contribution of unshaded road and carpark surfaces to local heat island effects. In March 2020, 14,700 m2 of road and carpark surfaces were coated with a highly reflective asphalt emulsion in the local government areas of Blacktown, Campbelltown and Parramatta to reduce surface temperatures of pavements. The trial was accompanied by an environmental monitoring program. The program used measurements of surface, air and black globe temperatures to document the effectiveness of the surface coat on cooling. Data were collected between February 2020 and March 2021 using a full-factorial design with paired impact and control sites. Results showed that surface temperatures of unshaded coated pavements were on average 6°C and at maximum 11°C cooler compared to uncoated pavements. Tree shade reduced temperatures of uncoated surfaces by 20°C and that of coated surfaces by 14°C leading to identical surface temperatures in the shade on coated and uncoated surfaces. Surface coating did not systematically reduce air temperature during the day or night. Back globe temperatures during sunny days increased by 2.7°C on coated compared to uncoated sites as a result of increased reflectivity of the surface. The higher exposure to reflected solar incident radiation resulted in lower thermal comfort in the sun on coated surfaces. The Cool Roads Trial established important information for the management of heat in Western Sydney and beyond. Increasing albedo of roads and carparks will help reduce surface Urban Heat Island Effects due to lower surface temperatures. Ambient air temperatures were not lowered as a result of coating roads and carparks, which can potentially be a matter of scale. The Cool Roads Trial worked at the microscale where air cooling benefits could be masked by continuous mixing of local with surrounding air masses. The range of thermal effects documented in this report make it clear that mitigating the impacts of urban heat will require a broad suite of solutions. A clear definition of desired thermal outcomes will be necessary on a case-by-case basis. Only once thermal outcomes are defined can resilience of urban populations, infrastructure and ecosystems against intensifying summer heat be improved effectively

The best urban trees for daytime cooling leave nights slightly warmer

Summer air temperatures will continue to rise in metropolitan regions due to climate change and urbanization, intensifying daytime and nighttime air temperatures and result in greater thermal discomfort for city dwellers. Urban heat may be reduced by trees which provide shade, decreasing air and surface temperatures underneath their canopies. We asked whether tree height and canopy density can help to identify species that provide greater microclimate benefits during day and night. We also asked if increased canopy cover of street trees provides similar microclimate benefits. We used continuous measurements of near-surface air temperatures under 36 park trees and from two urban streets to assess these questions. In the park, trees were grouped according to their height (20 m) and canopy density (low, high), while the effect of canopy cover was tested using streets with high (31%) and low (11%) cover. Daytime near-surface air temperature declined with increasing height and canopy density providing significant cooling benefits. However, this trend was reversed at night when tall trees with dense canopies restricted longwave radiative cooling and trapped warm air beneath their crowns. High canopy cover of street trees reduced daytime air temperatures more, resulting in a lower number of days with hot (>35 °C) and extreme (>40 °C) air temperatures compared to the street that had low canopy cover. These findings suggest that tree species and streetscapes with dense canopy cover improve local thermal conditions during the day but do not seem ideal to allow for nighttime cooling, creating potential discomfort for residents during hot summer nights. Our results indicate that classifying trees using a simple metric can assist in selecting tree species that can alleviate the local negative effect of urban heat during the day, but at the same time, their effect in preventing optimal longwave radiative cooling during the night must be factored into planting strategies

Benchmarking Tree Canopy in Sydney's Hot Schools

This project identified the 100 most vulnerable schools to heat in Greater Western Sydney using a newly developed Heat Score. The Heat Score combines socio-economic information that captures exposure, sensitivity and adaptivity of local communities to heat with environmental data related to surface and air temperatures of urban space. Following the identification of the 100 schools, high-resolution aerial imagery was used to remotely measure a range of attributes at each school. These attributes included the area covered by buildings and open space, as well as the area of tree canopy cover and manmade shade structures. We determined the size of close to 5,000 individual objects to establish a benchmark of shade in Sydney’s hot schools. Key findings: » Mean area covered by the 100 schools is 23,000 m². » On average 18% of that area is shaded » Tree canopy cover makes up the majority (15%) of the shaded area. » Tree canopy cover increases with the area covered by a school. » Public schools tend to cover larger areas and thus have more tree canopy cover compared to Catholic and independent schools. » Urban Heat Island effects were reduced when the area of shade was increased. Additional tree plantings will provide microclimatic benefits. However, the present study reveals that a dual approach is necessary to increase canopy cover among the target schools that differentiates between needs and opportunities. Catholic and independent schools have the highest need for additional tree canopy cover as their current cover is low. These schools tend to have less open space available for plantings. Successful strategies will require establishing low numbers of carefully selected trees at strategic planting locations to deliver the greatest local shading and cooling benefits. Public schools offer the greatest opportunities for mass planting of additional trees as they have large areas of open space available. Planting sizeable clusters of trees will provide the greatest cooling benefits not only for the school but generate microclimate and environmental benefits for the surrounding communities. Analyses provided in this report will assist the development of the most effective tree planting strategies for each of Sydney’s 100 hot schools

Outdoor playgrounds and climate change : importance of surface materials and shade to extend play time and prevent burn injuries

Surfaces in outdoor playgrounds get hot in the sun and can cause serious skin burns in children. In-situ measurements from 10 playgrounds in Sydney showed that the maximum and average surface temperatures of sunexposed playground equipment and flooring surfaces were frequently above skin contact burn thresholds. Black and dark-coloured wet pour rubber and synthetic turf were the hottest floor materials, all having maximum surface temperatures (Ts_max) > 80 ◦C. A blue rubber dolphin was the hottest piece of play equipment, with a Ts_max of 91.8 ◦C. A systematic assessment of common synthetic flooring materials exposed to full sun showed notable differences in Ts_max between material types and colour-tones. Synthetic turf with 40 mm long grass blades (STlng-GR) was the hottest material (Ts_max = 84.5 ◦C), followed by dark blue styrene butadiene rubber (SBRD-BL, Ts_max = 81.1 ◦C), dark green ethylene propylene diene polymer (EPDMD-GR-2, Ts_max = 77.8 ◦C), dark brown thermoplastic vulcanizate (TPVD-BR, Ts_max = 71.8 ◦C), and intermediate blue thermoplastic polyolefin (TPOI-BL, Ts_max = 65.0 ◦C). All these materials were hot enough to cause contact burns on typical, warm summer days when children are likely to visit outdoor playgrounds. Surface temperatures were significantly reduced in the shade and never reached burn threshold temperatures. Selection of appropriate material type and colourtone, together with the provision of shade can remove the hazard risk for contact skin burns from outdoor playgrounds. Results of this work will assist playground designers and managers to provide safer places for our children to play longer in increasingly warmer summers

Despicable Urban Places: Hot Car Parks

Cities are warmer than surrounding non-urban areas. Climate models predict that metropolitan centres will become even warmer due to the dual impacts of global warming and densification. However, the outer fringe zones of metropolitan centres will also become warmer as a consequence of urban expansion that requires replacing green and open spaces like pastures or bushland with grey infrastructure such as roads and buildings. Limiting the warming effect of urban expansion is possible. It requires dedicated heat-responsive planning and design strategies being applied systematically and at scale. But where should planners and developers start to effectively reduce urban heat? At-grade car parks are an ideal starting point. They represent the ‘low-hanging fruit’ for urban cooling efforts. While unavoidable today and in the near future, at-grade car parks are predominately unshaded; made from black, heat-retaining asphalt; widespread and fairly uniform; and often large in size. Changes to current designs of at-grade car parks can therefore have a big impact. A number of strategies to effectively reduce surface heat of car parks are commercially available. Cooling car parks not only addresses their status as local heat islands, but it also leads to lower ambient air temperatures in downwind environments. This report documents:   Microclimates across eight car parks and reference sites covered by vegetation. Measurements of surface and air temperatures related to a range of car park surface materials. The cooling effect of shade in car parks. Current design guidelines and policies in Australia related to car parks. Alternative design solutions for cooler car parks. The empirical data and policy analysis are used to develop a set of recommendations for urban heat mitigation that can be applied to new and existing car parks. Because of the common nature of at-grade car parks around the world, the proposed cooling techniques can be applied globally, irrespective of the fact that the underlying case studies and data originated from Sydney

School Microclimates

Outdoor school environments need to be safe, stimulate physical and cognitive development of children and encourage learning. These key requirements are jeopardised by increasing summer heat. Summer heat limits outdoor activities and has adverse effects on physical wellbeing of school children and teachers. Children are particularly vulnerable to heat as they regulate their core temperature through convection, which becomes less effective when it is hot. Based on empirical data collections, this report provides more than 20 practical recommendations on how to reduce the impacts of outdoor heat. Although these recommendations were devised based on work around a public school in Western Sydney, their universal character allows applying them to any school or other urban build infrastructure. Avoiding the use of artificial grass in unshaded spaces, shading black asphalt, allowing natural air flows and using shade materials with highly reflective upper surfaces should be fundamental principles in design and building guidelines for heat-smart schools

Benchmarking Summer Heat Across Penrith, New South Wales

This report documents variation of summer temperatures across the Local Government Area of Penrith in Western Sydney. Between 14 December 2019 and 31 March 2020, more than 1.4 million measurements of air temperatures were collected using 120 data loggers. The network of data loggers covered the entire Local Government Area from Emu Plains in the west to St Marys in the east and Agnes Banks in the north to Badgerys Creek in the south. Analyses of these data revealed that local populations of Penrith experienced air temperatures of more than 50°C during three individual days.Throughout the summer of 2019/20, Emu Plains was the warmest and Mulgoa the coolest suburb. Nighttime air temperatures were higher in suburbs with high cover of hard surfaces compared to those where open surfaces dominated, demonstrating clear Urban Heat Island Effects in the area. An Urban Heat Island was also detected for the town of St Marys, where the urban core remained up to 2.4°C warmer during the night compared to the surrounding residential neighbourhoods. A wide rage of temperature analyses provide a nuanced picture of how summer heat is impacting this important city in Western Sydney. A total of 12 clear recommendations developed with the help of the empirical work

Measuring local-scale canopy-layer air temperatures in the built environment : a flexible method for urban heat studies

To reduce increasing human morbidity and mortality due to urban overheating, urban cooling strategies need to be targeted towards intra-urban hot spots. The application of findings from numerous urban heat studies is limited because methods do not measure air temperature relevant to the human experience with a sufficient level of data granularity. In this work, we developed and tested a unit consisting of a temperature data logger and a custom-made weather shield that is substantially less expensive than published alternatives and can be deployed with high spatial flexibility to measure canopy-layer (near-surface) air temperature relevant to people living in the built environment. Accuracy of results was compared with a more expensive, commercially available scientific instrument as well as official Bureau of Meteorology weather stations in Sydney, Australia. The unit costs around 15% of the price of the tested alternative and only 25% of the least expensive published alternative. Data quality was almost identical to that provided by more expensive scientific instruments and official weather stations. Temporal and spatial coverage and the resulting granularity of air temperature data were very high. The air temperature measurement method reported here can be used in future urban heat studies to determine intraurban hot spots. Resultant knowledge can be used to target cooling strategies that maximise benefits to the human population, reducing heat-related illnesses and death in overheating cities

Leaf age and eCO2 both influence photosynthesis by increasing light harvesting in mature Eucalyptus tereticornis at EucFACE

Only a few previous studies have examined how photosynthetically active radiation absorptance, pigments and electron flow change in mature trees exposed to long-term increase in CO2 concentration. We investigated pigment concentrations, leaf optical properties and quantum yield of old and new leaves exposed to ambient (aCO2) and elevated (eCO2) CO2 treatments. Leaf absorptance was around 90% in E. tereticornis trees across both foliage age classes and CO2 treatments. New leaves had 15% higher quantum yield with increased absorptance within the blue spectrum than old leaves; while they reflected and transmitted more photons. In addition, young foliage had increased mass-based concentrations of chlorophyll and carotenoids; however, pigment concentrations were reduced when expressed on area-basis. Quantum yield was 9% higher in eCO2 than aCO2 across both foliage age classes. The CO2 effect was stronger in new leaves where the quantum yield was 17% higher in eCO2 than aCO2, but not different in old leaves between CO2 treatments. New leaves had higher transmittance of photons in eCO2 than aCO2, while there was no change in old leaves. Mass-based concentrations of chlorophyll and carotenoids were reduced in eCO2 compared to aCO2 while concentrations of anthocyanins were higher in response to CO2 treatment. There was a significant effect of Age x CO2 interaction on ratio a/b with larger eCO2-related reductions in old leaves (–5%) but no change in new leaves. Generally, new leaves were more efficient in utilizing the absorbed photons than old leaves, especially under eCO2 which resulted in more carbon fixation. This implies that leaves can adjust their light harvesting capacity to eCO2, particularly in younger leaves which have higher photosynthetic activity