Study Findings

• All three cool road sealants showed a reduced surface temperature when compared to the portion of traditional asphalt road used as a control.
• Cooling demonstrated by each product was 8.65°C (CoolSeal), 4.95°C (JetBloc) and 2.6°C (JetCool) during the day and 4.2°C (CoolSeal), 2.9°C (JetBloc) and 1.5°C (JetCool) during the night.
• New/darker traditional asphalt road nearby was found to be hotter during the day than the cool road sealants, but also 6°C hotter than our control asphalt that was more aged.
• Measuring the impacts of these sealants on air temperature proved challenging and was inconclusive.
• Widespread use of the most effective sealant could generate a near 1°C surface cooling at a whole of city scale. While this level of surface temperature cooling across the urban area may not seem substantial it could improve human comfort level and reduce building energy consumption.
• Modelling of an increase in tree canopy to cover 33% of roads in Adelaide was predicted to achieve a similar level of surface cooling and would be likely to deliver a higher human comfort due to shading and other benefits of trees.
• There was widespread interest in the cool road trial across the community with strong engagement though social media. While survey response numbers were low, the responses were mostly positive with no negative feedback regarding the products.
• All three cool road sealants are road preservation products, 6 months after application they were all seen to be providing a full seal coating of the road surfaces, however, the sealants had begun polishing off the top of the stone aggregate of the existing oxidised asphalt surface. The visual appearance was better when the products were applied onto new asphalt.

Background

The urban heat island effect is an extensively documented climate phenomenon and is prevalent in many Australian cities. Concrete buildings and asphalt roads create heat islands that can be significantly hotter than temperatures in the surrounding suburban and rural areas. Because the number of extreme heat days is predicted to increase significantly over the next few decades, and the urban heat island effect has been shown to be exacerbated by climate change, the City of Adelaide is working to understand and reduce heat islands.

A Heat Mapping Tool is publicly available which assesses how all suburbs are affected on hot days and nights. The City of Adelaide is using this data to inform its planning and design, for example in tree planting and choice of materials in public spaces like playgrounds, parks and pavements. Residents and businesses can consult the tool to understand how heat exposed their property is.

You will find a graph in the image gallery that depicts the average land surface temperature for a range of different surfaces measured across the Heat Mapping study area. Bitumen is one of the consistently hot urban surfaces both day and night, covers a large part of our city, and is directly controlled by the City of Adelaide.