How city planners save urban dwellers from the heat

    02 Sep 2021

    Global temperatures are rising, and 2020 is the hottest year on record. Since the 19th century, the planet has warmed by more than one degree Celsius, which is especially noticeable now in large cities. In a built environment that is too often made of glass, steel, asphalt, and concrete, hazardous urban heat islands increase the risk of heatstroke, Urbanarch writes (the article was originally published on The Dirt.). The poorest and most marginalized communities are at particular risk, as they tend to live in disadvantaged areas lacking trees and green spaces to mitigate the effects of the heat.

    According to Devanshi Purohit, associate director of urban design at CBT Architects, extreme heat is the number one climate killer in the United States. More people die from heat than from rising sea levels, floods, droughts, and other extreme weather events. But, oddly enough, the intense heat doesn’t get the attention it deserves. The reduction of so-called urban heat islands should have long been the focus of planning and design professionals.

    In three cities – New York, Copenhagen, and Abu Dhabi – new approaches have been developed o reduce urban temperatures and help communities adapt to a hotter world.

    New York has a city government that focuses on sustainability, there is a Mayor’s office of resilience, and Daphne Lundi is deputy director for social resilience. Lundi seeks how to leverage communities’ support systems to lower risks to climate impacts.

    She said that on average, in cities, it can be up to 12° C hotter than in the surrounding natural areas. In addition, apartments and houses without air conditioning can be 11° C hotter than outside. This is why there are over 1,100 hospitalizations and over 100 deaths due to heatstroke in New York every year.

    Risk levels can vary significantly from area to area. Thanks to the Thermal Vulnerability Index, which was developed in partnership with Columbia University, the City now understands that 3.4 million New Yorkers are highly vulnerable.

    “Risk is based on environmental factors such as the amount of green space, but is also linked to poverty and race,” Lundy explained. Her department determined that black, low-income residents and the elderly are most likely to get sick or die from extreme heat.

    In 2017, New York launched the Cool Areas program – its first plan to tackle extreme heat – and set aside $100 million for targeted investments in green infrastructure and tree planting in high-risk areas.

    Those who are housebound and have severe physical and mental problems are in the most dangerous situation. In this way, the city is adapting to existing risks by training domestic helpers. Their mission is to help the elderly and other particularly vulnerable people identify “early signs of early heatstroke and illness.”

    New York City also launched the Be a Friend Campaign to support New Yorkers’ most difficult-to-reach people. During the heatwave, the program uses “long-standing connections” and activates a system where people check on neighbors who do not leave their homes. “The system uses proven means of communication. They were also used during the pandemic, ” he says.

    Authorities paint the roofs of municipal properties white to reflect more heat into the atmosphere. They also facilitate access to so-called cooling centers, where people can simply take a break from the sweltering heat. The authorities bought air conditioners for low-income people vulnerable to heat.

    The city has already installed 74,000 air conditioners in homes. It has also created a utility assistance program that offers a subsidy of $30 a month during the warmer months to make these new air conditioners actually use.

    After moving to Denmark, Rasmus Astrup, design director, and partner at SLA, landscape architecture and urban design firm, explained that cities, with all their warming surfaces, are actually part of the climate problem because they increase thermal exposure and generate more heat.

    “Cities as they are designed now are very unreasonable and pose a lot of new problems,” he says.

    But nature is self-sufficient, and it offers the best strategies for dealing with extreme heat. “Nature is the smartest, so we need to rethink cities and make them more environmentally friendly,” says Rasmus Astrup.

    He noted that it is a matter of ecology in general, and not just the amount of greenery in cities, because climate change is also a denier. But it affects biodiversity, which underlies all life on earth. Ecological urban solutions are needed not only to combat heat islands but also to maintain biodiversity.

    Astrup focused on one of the Copenhagen squares as a solution to several climate problems: heat, floods and loss of biodiversity. In just a few decades, “Copenhagen will have a climate similar to Barcelona,” so Astrup believes that such places are needed as many as possible.

    A standard roundabout in an area with very little greenery has been converted to a forested area with integrated cycle lanes and tram lines.

    Astrup described the project as “blue-green climate adaptation,” resulting in a biodiverse landscape that skillfully reduces heat and manages storm water. “There is now a green area around every corner.”

    Kishore Varanasi, Head of Urban Design at CBT, argues for evidence-based design to solve thermal problems.

    “We’ve gotten hotter, but what strategies can we use to tackle the problem? Buildings, cars, asphalt all make cities even hotter, so we need a multi-layered strategy to eliminate heat sources,” he says.

    There are approaches based on shading, evaporation, conduction convection. For Varanasi, the Universal Thermal Climate Index is a helpful tool for measuring the heat in the environment and its impact on us.

    “We can comfortably withstand temperatures up to 30 ° C, but not much more,” says Kishore.

    In Abu Dhabi, summer temperatures can be extreme as early as the late morning, outside of people’s comfort zones. To reduce heat stress, CBT works with stakeholders to create “cool trails and cool zones.”

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    Given that Abu Dhabi does not have enough water to grow large trees, CBT has developed shaded architectural structures to provide “intermittent shading.” For example, a pedestrian walking along a path will be in the shade for one minute and then in direct sunlight for one minute. “People can withstand a minute of intense heat.” The structures are also angled to provide shade at different times of the day.

    Varanasi said the spaces between buildings could be converted into cool zones effortlessly. There are many ways – vertical shading, green walls and reflective coverings, as well as thermally comfortable zones that can be “delightful at night”.

    Lundi notes that new developments are often designed with climate resilience in mind, but cities are made up mostly of older homes. “We also need to move our old neighborhoods into the future.”

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