Last month saw the UK sizzle with some of the the hottest days recorded in 40 years and as heatwaves swept the country, cities were hit the hardest.
Urban landscapes of asphalt, brick, metal and dark rooftops soak up an enormous amount of energy from sunlight and reflect even more light. This energy absorption leads to an urban heat island (UHI) where cities experience higher-than-normal heat temperatures, as compared to surrounding areas. In this article, we take a look at changes that could be made to our built environment to contribute to a drop in temperatures over the summer months.
What is an urban heat island?
According to the Met Office, an urban heat island (UHI) is “a man-made area that’s significantly warmer than the surrounding countryside, especially at night.”
In fact, the temperature of a city whose population
is over 1 million can be 1-3°C more than outside the urban environs. In the evening, the difference can be as high as 12°C.
Elevated temperatures from UHIs can adversely affect a community’s environment and quality of life by increasing energy consumption and air conditioning costs, elevating greenhouse gas emissions and air pollution, posing dangers to the aquatic systems, causing potential heat-related discomfort and danger to human and animal health, and posing secondary impacts on weather and climate.
There are several ways in which the effects of UHIs can be reduced – let’s take a look at some of them.
Light-coloured roofs reflect 50% more light
City rooftops are typically black because the traditionally-used asphalt and tar are waterproof, tough, ductile and easy to apply to complex rooftop shapes and designs.
However, black and dull colours absorb lots of solar heat, which results in warmer surfaces. To mitigate the problem of urban heat islands, more people are having bright, white roofs installed.
The use of light-coloured concrete and white roofs is far more effective in reflecting up to 50% more light and lowering the temperature. Additionally, light-coloured concrete and white roofs reduce the overall air conditioning demands (and costs).
Green roofs for sustainability
Green roofs are a great, sustainable option for reducing the temperature in the city.
Green roofing is the practice of planting vegetation on a roof to act as perfect insulators, cooling the surrounding environment and reducing demands for air-conditioning. Plus there’s the added bonus that air quality will improve since plants absorb carbon dioxide and produce fresh air.
Plant trees to reflect solar radiation
The practice of tree planting within and around cities is an excellent way of reflecting solar radiation, while also decreasing the urban heat island effect.
Trees provide shade, absorb carbon dioxide, release oxygen and fresh air and provide a cooling effect. Deciduous trees are ideal for urban areas because they cool the area in summer and don’t block any warmth during the wintertime.
Awareness and implementation of heat reduction policies and regulations
The EU directives regarding environmental policies, such as low carbon fuel standards and the use of renewable energy, can significantly regulate and mitigate the problems of the urban heat island effect.
With fewer emissions, the level of greenhouse gases in the atmosphere can be reduced. This, in turn, decreases the effects of climate change and global warming. Education and community outreach can also help to ensure that communities are made aware of the economic and social benefits of sustainable practices such as planting trees, and eco-roofing/paving.
Use harvested rainwater for cooling
Implementing Q-Bic Plus infiltration systems is one way to tackle the issue of excess rainwater.
What many don’t know is that the system can also be used for water attenuation. When rainwater is harvested you can re-use that water in many ways during dry spells:
Q-Bic Plus has been used to create a high-performance stormwater management system for a new park in central London. Find out more about this case study here.
