Cool Parks

CP1: Shade

6 default credit points

Outcome

Shade (natural and built) lowers surface radiative temperatures, promotes ventilation, and improves Human Thermal Comfort.

Criteria

Retain existing trees:

• Existing trees that are ecologically or culturally significant or have a trunk diameter >300mm and that are in good condition and are locally appropriate are retained in-situ.

And;

Tree canopy cover (at maturity):

• Parks < 5ha without sports courts and fields: >45% tree canopy cover.
• Parks < 5ha with sports courts and fields: >45% tree canopy cover applied to the park area excluding sports courts and fields.
• Parks > 5ha: No net-loss of tree canopy cover compared to existing (baseline).

And;

Shading of high use spaces (e.g. children's playgrounds and BBQ/eating areas):

• >70% shade cover (measured in plan).

Guidance

• Urban parks cool more effectively if they contain scattered trees and receive irrigation.
• Prioritise provision of canopy shade for parks where daytime cooling is the priority (e.g., parks within city centres, commercial areas and low-rise residential developments).
• Prioritise more open green areas (shade trees planted to park edges) for parks where night-time cooling is the priority (e.g., parks in higher density residential areas).
• A heterogeneous tree canopy planted in groves is preferred to a homogeneous tree canopy planted in continuous rows.
• In the right positioning, well shaded and irrigated parks can provide down-wind cooling effects beyond the park boundaries (see also UD4 and UD6).
• Trees have the greatest urban cooling effect when they are positioned to shade hard surfaces during the hottest times of the day.
• Selection and placement of shade solutions within parks should consider peak-use times to ensure shade maximises solar UV protection when it is needed most.
• Tree species selection to suit in-situ soil conditions and resilience to high heat stress having regard to projected future extreme heat days due to climate change (refer to Adapt NSW's Regional Climate Change Snapshot Reports for a summary of projected changes to extreme heat days, temperatures and summer rainfall in your region).
• Access to deep soils (a landscaped area connected horizontally to the soil system and local ground water system beyond and is unimpeded by any building or structure above or below ground) supports healthy trees. Recommended minimum deep soil areas (assuming 600 to 1000mm accessible soil depth for clay and sandy loam soils respectively):
  • Small Trees (6 metre canopy diameter at maturity): 14m² in sandy loam soils; 23m² in clay soils.
  • Medium Trees (8m diameter canopy at maturity): 18m² in sandy loam soils; 30m² in clay soils.
  • Large Trees (≥12m diameter canopy at maturity): 26m² in sandy loam soils; 43m² in clay soils.
• A variety of suitable tree species is preferred to increase the urban canopy roughness through different tree heights and foliage types.
• Guidance on the best tree species for a given geography based on various planting factors including future climate is available on the https://www.whichplantwhere.com.au website.
• Use evergreen trees for areas that will benefit from year-round shade.
• Use deciduous trees where sunlight is desirable in winter.
• Consideration of safety is paramount with species selected to minimise risk to public safety.
• Ensure a secure water supply is available during extended dry periods to provide the minimum sustaining irrigation needs of each tree species.
• Provide active management of younger trees to support crown development.
• Develop and apply long term strategies to transition from built shade to an increased proportion of natural shade as canopy increases in size and density.
• If installing shade sails as part of built shade solutions, make sure to choose fabric that has a UV Effectiveness (UVE) rating of 80% or more.
• A test if shade is high quality or not on a clear day is the amount of blue sky you can see (sky view factor) while underneath it. The less blue sky you can see, the better protection from solar UV radiation.

Evidence Requirements

• A baseline tree survey covering species (including ecological and/or cultural significance), size, condition, and canopy cover.
• Landscape plan(s) showing retained trees and proposed trees with planned mature canopy area provides as % of gross park area (excluding sports courts and fields).

Science Rationale

• High quality built and natural shade can reduce exposure to solar UV radiation by up to 75% (57).
• Common surfaces used in playgrounds can climb to temperatures of up to 60°C during the day. Providing shade can reduce the temperature of these surfaces by 20°C (58).
• Radiant temperatures in parks that have well-irrigated trees can be 2-4°C cooler than adjacent un-vegetated or build up areas; the extent and proportion of tree plantings can have a 1-2°C impact on the actual temperature.
• Trees deliver greater cooling effect and enhance human comfort more than other urban green approaches (shrubs, grass) (39). Existing established trees provide the greatest benefit for heat minimisation and should be prioritised in planning.
• Trees that are water stressed will lead to reduced plant transpiration and reduced cooling potential (31).

Related Credits

• UD2 - Wind buffering / filtering
• UD4 - Green and blue open Space
• UD5 - Retention of existing tree canopy
• UD6 - Water Sensitive Urban Design
• CS2 - Irrigation
• INV2 - Data collection and Analysis

References

(31) Norton, B., Coutts, A., Livesley, S., Harris, R., Hunter, A., Williams, N. 2015. Planning for cooler cities: A framework to prioritise green infrastructure to mitigate high temperatures in urban landscapes., Landscape and Urban Planning, Vol. 134.

(39) Coutts, A and Tapper. N. Trees for a Cool City: Guidelines for optimised tree placement, 2017. Melbourne Australia: Cooperative Research Centre for Water Sensitive Cities.

(57) Parsons, P., Neale, R., Wolski, P. & Green, A. 1998, ‘The shady side of solar protection’, Medical Journal of Australia, 168: 327-to330

(58) Pfautsch, S., Rouillard, S., Wujeska-Klause, A., Bae, A., Vu, L., Manea, A., Leishman, M. (2020). School Microclimates.https://doi.org/10.26183/np86-t866