The urban heat island effect occurs when pavements, roads, and buildings absorb the sun's heat and radiate it back, causing the temperature to increase and preventing the city from cooling down. With the growing reliance on cars in cities, the number of urban car park spaces is also increasing to accommodate buildings. This has resulted in the conversion of large areas of pervious land covered with vegetation into impervious hard surfaces for more car parks. The use of materials like asphalt, combined with the lack of shade, reflective steel surfaces of parked cars, and loss of greenery in these extensive car parks, contributes to the amplification of high-temperature effects and extreme heat events, making urban spaces uncomfortable. This transformation is impacting the climate of car-dependent regions and calls for collaborative ideas and efforts to mitigate the negative effects of rising heat.
Cool Materials
Urban areas, such as cities, tend to be warmer than natural areas. This is mainly due to the different properties of the materials used in the construction of roads, pavements, and buildings compared to natural land cover. At-grade car parks, in particular, contribute to the urban heat island effect and impact microclimates. They are often unshaded, made of heat-retaining asphalt, widespread, uniform, and large.
Research from the University of Western Sydney sheds light on the role of asphalt car parks in exacerbating the urban heat island effect. Asphalt has a high heat retention capacity, leading to increased temperatures in the microclimate during both day and night. To combat this, the report titled "Despicable Urban Spaces: Urban Car Parks" by Dr. Sebastian Pfautsch highlights effective cooling techniques for urban car parks.
The foundational solution for cooling down existing car parks is to replace the materials used. This includes reducing the area covered by impermeable black asphalt, coating the remaining asphalt areas with reflective surface sealants, increasing open spaces with permeable pavements, and using solar reflective and porous surface materials. Implementing these strategies will transform impermeable car park surfaces into pervious ones, creating a cooler atmosphere.
Green Spaces
Trees have numerous benefits, such as providing shade to reduce heat exposure and helping us withstand hotter temperatures. When these trees are aggregated and form parklands, they not only provide local cooling but also minimize the impact of heat on people. To manage the impact of increased urban temperatures, it is important to create more thermal oases within urban car parks. Dr. Sebastian Pfautsch emphasizes in his report that car parks should be designed in a way that preserves existing trees and strategically utilizes them as tree canopies for shade. Other methods to cool down urban spaces include transplanting trees to existing car parks, planting new trees, and introducing green infrastructure for strategic shading. It is also beneficial to identify tree species that thrive in sparse urban spaces. Urban car parks can greatly benefit from climate-adapted tree species with wide, dense crowns to provide shade over larger areas.
The growing number of unshaded car parks, particularly on the urban fringe, is a symbol of our failure to create communities fit for the 21st century. They reflect an unwillingness to stop outdated and unsustainable urban sprawl and associated car dependency. Worse, these spaces will be with us for decades. In a warming world, improving the design of new and existing car parks is essential. Regulations and guidelines need updating. Shadeless, heat-radiating car parks must become relics of the past. Dr Sebastian Pfautsch
Blue Infrastructure
Similar to green spaces, blue infrastructure refers to water bodies such as ponds, rivers, and dams, which can effectively reduce temperatures. Integrating water features with green spaces can further contribute to the cooling of surrounding areas. By strategically placing blue infrastructures alongside greenery and wind corridors, the breeze that passes over the water bodies is cooled and carries this cooling effect to nearby areas. Additionally, blue infrastructure can be utilized as irrigation systems for green infrastructure in car parks. These systems can be active or passive, functioning as fountains or mist infrastructure to lower temperatures in car park areas.
Better Climate-Responsive Urban Planning
Individual solutions to cool down car parks, when implemented within poor climate-responsive urban planning, would not be effective. The temperature regulation in urban areas is greatly influenced by urban design and planning decisions. Designing street canyons to promote shade and ventilation can reduce local air and surface temperatures, improve outdoor thermal comfort, and play a key role in cooling our cities and people. When it comes to car parks, they should be integrated into the urban system, serving multiple buildings in an area and allowing room for more green infrastructure. Climate-responsive policies specific to car parks' urban planning should also be implemented. This involves making design decisions that prioritize cool urban spaces, walkability, and eco-friendly cities.
Furthermore, urban design that incorporates open spaces, strategic building positioning, and a combination of blue infrastructure and greenery can facilitate natural cooling and help dissipate heat in cities. In Singapore's urban planning, networks of wind corridors demonstrate how thoughtful planning can create a mutually beneficial relationship between thermal oases and ventilation. Similarly, in Sydney's eastern suburbs, the sea breeze effectively cools the area, while in the western suburbs, creating ponds and parks can have a similar cooling effect on the breezes that flow through the area.
To further reduce the impact of car park heat on urban microclimates, several other singular measures can be implemented. One approach is to use solar panels to shade car parks, which not only provides relief from the heat but also generates renewable energy. Another strategy is to implement green or living facades for multi-level parking lots, incorporating vegetation to cool the area. Infrastructure for active and public transportation can also limit car use, reducing the number of cars in parking lots. Conducting occupancy surveys can help identify the optimal size of car parks and available space for cooling mechanisms. Transforming unused car parks into green spaces or parks can contribute to cooling urban areas and providing more greenery. Additionally, increasing smart and shared parking options for both private and business use can help alleviate the heat impact of car parks. These strategies demonstrate the need for a multi-faceted approach to address the issue of cooling down large urban car parks. Moreover, considering high technological solutions like urban air conditioning and smart cooling transfer can further mitigate the negative effects of rising heat and effectively cool down urban car parks.
