Urban heat islands (UHIs) are areas with significantly higher temperatures than surrounding regions. Heat retention and generation in the city center contributes to climate change and worsens air quality for people living in and near heat islands. They also negatively impact precipitation downwind of UHIs. UHIs are also the leading cause of weather-related deaths in the United States. Cities with inadequate nighttime cooling experience an increase in heat-related deaths during periods of hot weather, the majority of which are related to with UHI .
The reasons are many, but fortunately, solutions exist to combat their negative impacts on the population and the environment. Some of these solutions are doubly attractive because they simultaneously address other urban issues, such as quality of life and waste disposal. food deserts. They help make cities more attractive and livable for both residents and visitors. Here are ten ways to mitigate the harmful effects of UHI and create better cities for present and future generations.
10. Creation of additional pocket parks
The transformation of abandoned or neglected urban properties into small parks, called pocket parks by urban planners and architects, has proven effective in combating the problem of heat islands. After World War II, Athens, Greece, experienced a housing boom during which a number of apartment buildings replaced individual houses with surrounding greenery. Beginning in the late 1990s, Athens has begun implementing projects The project involved creating pocket parks on small, abandoned lots, in alleys, and stables. Roads intended for cars were also converted into green spaces with paths for pedestrians and cars. The expansion of green space helps cool the city and improve air quality.
Other cities have seen the value of pocket parks, including their contribution to quality of life by offering convenient opportunities to relieve urban stress. There are dozens in Chicago There are many such small parks, and there are plans for more. Mexico City built about 3.5 acres of small pocket parks scattered throughout the city, including in abandoned spaces under bridges and overpasses. Paris is known for its wide boulevards and open spaces, but he also embraced pocket parkas as part of long-term urban planning.
Pocket parks alone aren't a solution to UHI, but they can and do contribute to reducing heat retention in city centers. At the same time, they offer small oases of peace and relaxation without leaving the urban area. Their use influences urban planners both in terms of quality of life and in their efforts to create more heat-retentive urban centers. Whether in a large international city or a mid-sized one, they are an effective tool against UHI.
9. Create roofs that reflect rather than absorb heat.
Dark colors absorb heat, while light colors reflect it. Therefore, it makes sense that dark-colored roofs absorb heat during daylight hours and release it during the relatively cooler hours of the night. The slowly released heat remains, for the most part, in a bubble above the surface, thus creating the UGI image. On a day when the ambient temperature is 90 degrees, the temperature of a dark, heat-absorbing roof can exceed 190 degrees . The dense concentration of such roofs traps a lot of heat, which contributes significantly to the increase in the temperature of the UHI compared to the surrounding rural areas.
Reflective roofs are an obvious solution to heat retention. And, like pocket parks, they offer other benefits as well. They can reduce the building's internal temperature, reducing the need for air conditioning. Absorbed heat damages roofs; reflected heat reduces roof wear and tear and helps extend their lifespan. Thus, cool roofs benefit society, as well as the owners and residents of the buildings on which they are installed.
Beginning in 2012, volunteers in New York City began painting dark roofs white in an attempt to reduce heat retention in the city. As of 2018, they had painted nearly 7 million square feet of previously dark asphalt roofs, a lot of paint and time were spent. Even with these efforts, 99% of the city's roofs remained untreated, demonstrating the severity of the problem.
8. Creating rooftop gardens and farms
Painting roofs white or covering them with reflective coating isn't the only way to make them cooler. There's a lot of empty space there. Using it as a space for growing greens Reduces heat absorption, improves air quality, and offers another benefit. Greenery in the form of fruits and vegetables can offer fresh, local produce in the city center. This isn't a far-fetched idea or a vision of the distant future. In a growing number of cities, urban rooftop gardening and commercial farms are becoming a reality.
In Montreal A grocer has converted its 25,000-square-foot rooftop into a farm growing tomatoes, herbs, beets, lettuce, and other vegetables. Grown in soil and irrigated by the store's dehumidification system, the produce from the rooftop farm is packaged and sold in the store below. In Tel Aviv, Israel Dizengoff Center, A large shopping center has a flat roof that supports two huge greenhouses where hydroponic vegetables are grown. During the growing season, it produces about 10,000 heads of cabbage lettuce per month for sale to customers outside the mall. He also grows a variety of other vegetables and, like in Montreal, provides a cooler roof for the buildings below.
Eagle Street Rooftop Farm Located above a three-story warehouse across the East River from Manhattan in Brooklyn, UHI's 6,000-square-foot growing space supplies produce for sale at its on-site farmers' market and to restaurants in the area. Like its Montreal and Tel Aviv operations, it also houses beehives for harvesting fresh honey. UHI's cooling by growing fresh produce on rooftops is a simple and easily achievable way to reduce urban heat, improve air quality, and provide access to fresh, locally grown fruits and vegetables.
7. Lighter road surfaces on streets and parking lots.
Anyone who walks across a paved parking lot on a hot, sunny day can attest to the fact that dark sidewalks absorb a lot of heat. Sidewalks are an integral part of any city, used by cars and pedestrians. A report from the U.S. Environmental Protection Agency states that from 35 to 40% of the average city's urban area is covered by pavement, making it the primary source of UHI. Cooler sidewalks are more difficult to achieve, as they cannot be covered with vegetation. Other factors, such as driver and pedestrian safety, visibility, and pavement durability, must also be considered.
Existing types of sidewalks can be treated with materials, such as coatings, to increase the amount of light reflected rather than absorbed. Other types have been studied for their suitability for future street, road, and parking lot renovations. One such option is permeable road surface, It has a higher density, allowing for greater convection during the day and reducing the amount of heat accumulated in the pavement for subsequent release. It also allows for better water absorption, reducing stormwater runoff during heavy rainfall. Lighter sidewalks also reduce the need for candlepower in street lighting.
Using cool sidewalks can reduce heat retention, leading to lower UHI temperatures, and improve visibility for drivers at night. There are concerns about cost. Replacing or modifying existing sidewalks in cities is a very complex proposition, and its implementation impacts traffic patterns, travel times, and other complexities of urban life. However, the potential benefits may well outweigh the costs if take into account general adverse effects of UHI .
6. Create better blue spaces in urban areas
Blue spaces are water within the city, whether flowing streams, lakes and ponds, or fountains and pools. Properly designed and maintained, they reduce heat islands. Improperly designed or maintained, they may worsen the situation . Water cools primarily through evaporation at the surface. But it also absorbs heat: the temperature of standing water rises during the day as sunlight warms the surface.
Artificial blue spaces, such as pump-powered fountains, can actually enhance the heat-retention effect, as the pumps create friction during operation. They also contribute to energy consumption, another source of heat retention. The cooling effect of blue spaces in cities is enhanced when it matches Using greenery, this effectively creates an island within an island, or a cool space surrounded by a larger UHI. The larger the number of such islands, the lower the overall amount of heat retained by the UHI.
More blue spaces in urban areas have been shown to provide benefits other than temperature reduction. It has been proven that life near blue spaces It reduces stress, improves physical activity and reduces obesity levels, which are significant benefits. Of course, to take full advantage of natural blue spaces like rivers, centuries-old runoff into water needs to be treated in many urban areas.
5. Plant more shade trees in urban areas.
The larger the shade canopy, the less sunlight reaches the city's heat-retaining surfaces. This applies not only to sidewalks and roofs, but also to the exterior walls of brick, stone, and concrete buildings, as well as the interiors of glass-walled buildings. Shade trees can also protect large areas of blue space, and the combination of increased blue and green space is one of the most effective ways to reduce daytime heat retention.
Urban parks and forests offer other benefits as well. Both quality of life and air quality are improved by large, shaded forested areas in cities. A 2014 study by the Georgia Institute of Technology found that Louisville, Kentucky, has one of the fastest-growing UHIs in the United States. It also found that the primary cause of increased heat was the lack of shade trees in many areas of the city, including the downtown area. The connection between shade trees and heat retention is clear. More trees = cooler city.
Cities typically lose trees for a variety of reasons, including pests, tree decay, new construction, and natural disasters like thunderstorms and winter snowstorms. A study from the Georgia Institute of Technology found that planting more trees and increasing shade canopy cover is the single most effective method for reducing heat accumulation and the resulting UHI. Simply put, trees and shade provide natural protection from potentially harmful sun rays and the heat they generate.
4. Vertical gardens improve air quality and reduce heat retention.
Vertical gardens are becoming increasingly popular in cities around the world, both for their aesthetic value and their economical impact on heat retention.In Singapore The 18 towers built for this purpose are covered in growing plants and illuminated by solar panels. The result is a dramatic display of vegetation that helps cool the city and simultaneously serves as a major tourist attraction. In Mexico City Officials have taken a more practical approach. The columns supporting bridges and overpasses are lined with felt, through which plants grow, irrigated by a dedicated rainwater collection system.
In Paris, the facade surrounding the entrance to Museum on the Quai Branly, Covered with more than 15,000 plants, the Athenaeum Hotel in London boasts seven floors of plants climbing the building's outer vertical corner. Besides the dramatic plant placement, vertical gardens cool the air, improve its quality, and protect the structure from heat absorption during sunny hours.
Beirut, Like other communities in Lebanon, it has also turned to vertical gardens to address UHI, air quality and landscaping issues. Vertical gardens are part of the solution to all three problems, but only when combined with other mitigation efforts. They also help reduce urban noise for residents, and plants act as a natural filter for rainwater. They can also be used for herbal production and other edible plants, although at the time of this writing they have not yet gained popularity in the United States.
3. Reduce traffic congestion
Automobiles and freight transport are the main contributors to UHI. Reducing their use clearly benefits cities, reducing both the severity of UHI and air pollutants. Lighter cars They also absorb less heat. Dark-colored cars in bumper-to-bumper traffic clearly negate the benefits of lighter-colored sidewalks.
But any attempt to reduce car use immediately raises controversy, especially in the United States. There, in large cities, it is common sit in traffic jams Much longer than the working day, and any government agency's decision to abolish dark-colored cars will be met with howls of protest over the infringement on personal freedom. Reducing car use will immediately lower the UHI temperature, but it's unlikely to happen anytime soon.
It's a scientific fact that vehicle emissions contribute to both air pollution and UHI, and this contribution increases in hot weather. Therefore, reducing traffic congestion is desirable if one wants to reduce the impact of UHI. There are other ways to reduce congestion without restricting the number of vehicles on the road. In the UK These methods are being studied and in some cases implemented.
2. Create cooler stormwater runoff to improve water quality.
Stormwater runoff from hot roofs and sidewalks has been shown to increase temperature of streams and lakes. Rising temperatures negatively impact aquatic life, both plant and animal. The result is unhealthy water that becomes lifeless and loses much of its cooling and filtering capacity. Deteriorating water quality is another consequence of UHI, affecting the lives of residents of urban areas as well as those living downstream.
One of the solutions One way to reduce the impact of stormwater is to create bioswales—sinks constructed into landscape features that can temporarily hold water, allowing it to cool before releasing it into streams. Permeable pavements, which cool the surface of urban areas, also absorb and disperse more water, rather than channeling it into storm drains. All of the mitigation efforts listed so far have a positive impact on cooling stormwater runoff, which will benefit streams and lakes.
Because river water flows downstream, the impact of UHI on water quality extends beyond the urban area, affecting aquatic biodiversity far from the heat source. The adverse impact of UHI on water quality is a major driver of urban cooling.
1. More efficient air conditioning can reduce UHI.
An air conditioner cools interior spaces by absorbing heat, which is released into the outside air. Cooling interiors heats the city in which they are located. Essentially, the heat (and humidity) inside the building is released outside. In a densely populated area on a hot day, a huge amount of heat is added to the outside air, creating a dome that captures sunlight, creating heat .
However, air conditioning and refrigeration are facts of modern life. More efficient methods of cooling air in buildings and vehicles will go a long way toward mitigating the impact of UHIs. They are being conducted research on more efficient air conditioning . If and when this is achieved, it will be just one of several weapons that future generations will use to combat the dangers of UHI.
None of the strategies on this list can eliminate UHI alone. But in various combinations, depending on local policies, community engagement, and environmental factors, several factors can have a mitigating effect on UHI, making cities more comfortable and, therefore, livable worldwide.