With temperatures set to soar across Europe this week, cities are once again facing the urban heat island effect – a common problem in metropolitan areas where the air temperature is significantly higher than in suburban areas. Citizens, city planners and government officials must prioritise finding cost-effective and efficient ways to keep our cities cool.
Urban planners need to rethink our cities from the ground up; this often is at a great public expense. The solutions available to make our cities greener – and cooler – have to compete with investment, human resources and physical space with other infrastructure projects. Councils are under pressure to demonstrate their limited resources are invested well in the short term, making it hard to put in long-term plans. But there are a wide array of options.
The most obvious one is to create more green spaces – everything from street trees and parks to green roofs and vertical gardens. A 10 per cent increase in tree canopy cover can lower afternoon ambient temperatures by as much as 1 to 1-5°C. Similar reductions can be achieved in parks with appropriate irrigation systems.
Water-based urban landscapes such as lakes, rivers and wetlands also have the potential to reduce city temperatures by 1-2°C. But in places like London where this isn’t easily achieved, various other technologies can help. For example, passive systems like pools, ponds and fountains are already being widely used in public spaces for both decorative and climatic reasons, while active or hybrid water components like evaporative wind towers, sprinklers and water fountains have been developed, tested and implemented in urban public spaces around the world.
The use of reflective materials can mitigate the urban heat island effect. Cool roofs and facades are building components with very high solar reflectance, while other common reflective materials applied to buildings are white and may be single ply or liquids such as paint or intelligent coatings, as well as natural materials including white marble.
The urban planning puzzle is made up of many pieces and entrepreneurialism is key to the challenge. Fortunately there’s plenty of energy in this space. For example, Vertical Field manufactures and installs sensor-controlled smart planters to purify the air from carbon dioxide, and when mounted onto buildings, they help insulate them from the sun and keep them cool. Another example is Lumiweave which has developed an innovative fabric that provides shade during the day and harvests the sun’s energy to illuminate itself and its surroundings at night, while TreeTube has developed a patented modular system of tubes that lets tree roots grow safely in a tunnel without disrupting their surroundings.
Technologies to reduce surface temperatures in cities are available but they require commitment from politicians. Many cities are yet to develop proper strategies on keeping cool. Large-scale transformation of the urban landscape requires determined and imaginative city officials who understand how to navigate a highly complex political process.
Cities like Amsterdam, which have traditionally been on the progressive forefront of urban planning, have a supportive public and sufficient funds to advance such projects. Cities where such public support is not a given -or where relations with the central government are strained – face the risk of their quality of life deteriorating at an accelerated pace.