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As heat waves worsen, cities are trying hard to stay cool

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With the country’s biggest cities seeing more extreme spikes in average temperature, leading planners and architects are getting creative to keep temperatures down

Air conditioners on a building in Park Avenue in New York City.
Air conditioners on a building in Park Avenue in New York City.
Peter Dutton: Flickr/Creative Commons

Between seemingly unrelenting heat waves, the punishing "heat dome" effect, and the gross reality of "corn sweat," this summer has been a particularly humid and miserable times in most major cities. From gross subways stations and stagnant airflow to the wilting impact of heat-reflecting pavement, downtown hasn’t just been hot. It’s felt unbearable.

The culprit is the heat island effect: dense development collects, reflects, and focuses summer’s heat. And as climate change continues to raise temperatures globally, it’s having an especially strong impact on urban areas. According to research from the Urban Climate Lab at Georgia Tech University, many of the country’s biggest cities are seeing more extreme spikes in average temperature that the surrounding suburban and rural areas, underlining the impact that concentrated development has on urban heat waves.

Cities are increasingly feeling the heat, and in response, architects, designers, and urban planners are finding ways to cool down, with many making climate mitigation a key part of long-term planning strategies. Earlier this year, the Design for Risk and Reconstruction Committee (DfRR) of the American Institute of Architects New York released Extreme Heat, a report suggesting ways that urban design and planning needs to adapt to coming temperature shifts. It’s a sobering read reflecting a new reality for urban America: unless this new design challenge is met head on, human health and comfort is going to be at increasing risk in a hotter world.

According to professor Anna Dyson, director of The Center for Architecture, Science and Ecology (CASE) at the School of Architecture at Rensselaer and one of authors of the report. "the large majority of urban heat island effects are accruing as a result of the replacement of natural systems or living systems with hard surfaces [and] engineered surfaces." That, of course, is the overall story of climate change. But cities face a particularly difficult challenge when it comes to cooling, since many of the natural remedies have been eliminated thanks to dense construction and the growth of air conditioning, which by consuming ever-increasing amounts of energy that generates the emissions responsible for climate change, creates a negative feedback loop.

"It is becoming an air-conditioned world," Lucas Davis, an energy economist at the University of California in Berkeley, told The Guardian. "The growth in air conditioning has been staggering. China is the sweet spot. The number of households that have it has doubled in five years. Every year, 60 million more units are being sold there, eight times as many as are sold annually in the United States."

Fire hydrant
A child cools off on the streets of Jackson Heights in Queens, New York.
Jorge Quinteros: Flickr/Creative Commons

According to Stan Cox, author of Losing Our Cool, which explores the ramifications of mechanical climate control, we have literally "built ourselves into a corner" with technology, creating an indoor ecosystem and car-focused transportation network dependent on artificial cooling.

"The biggest effect has been going from building design that emphasizes cross-ventilation to those with tight insulation," he says. "But it seems like everything that involves air conditioning has created undesirable feedback loops. There’s no way modern traffic systems, and our huge traffic jams, would be bearable without air conditioning. And one effect of artificial cooling is you’re able to pack more concrete, stone, steel and asphalt into a small area, and you have the urban heat island effect."

Manhattan offers a case study in how technology meant to cool ends up making us hotter in the long run: the dense development of modern high-rises, made possible by air conditioning, creates strips of concrete and steel that absorb heat during the day and radiate it back out at night. Cox says During the summer, Manhattan is often 7 degrees warmer due to the heat island effect.

Air conditioning, in effect, creates its own ecosystem. To cool off without sending carbon emissions off the charts—a huge potential crises as more and more people across the globe move to urban areas—cities need to promote and fund more natural methods of cooling off.

City planners have already been promoting numerous strategies to blunt the effects of increasingly warm weather. The Cool Cities Network, an alliance of planners focusing on ways to create more cool, reflective, and sustainable cities, recently released a set of more than 100 case studies, including a cooling section focused on programs that promote surface cooling and green roofs. Increasing green space and adding shade offer residents a respite, while promoting green roofs, reflective coverings, and the addition of photovoltaic panels can both reflect and absorb heat, while increasing green energy production.

Even small changes can truly add up: a study conducted by Concordia University suggests that by increasing the amount of white rooftops by just 1 percent across the globe, the adding reflectivity would provide enough of a cooling effect to keep more than 100 billion tons of carbon dioxide out of the atmosphere over the next century. A recent International Energy Agency report noted that investing in solar-powered air conditioning can cut cooling costs by up to 25%.

Luckily, many of the systemic changes and practices that can reduce pollution and cool cities sync up with the agendas of transportation and environmental activists. More sustainable zoning and building practices, from building up cycling infrastructure to promoting transit-oriented development, removes cars, pollution, and exhaust from the streets.

Oftentimes, the most effective solutions are the most simple. Many planners and park officials in cities such as Denver, Chicago, and Philadelphia have made a concerted push to restore and replant trees in an effort to provide a natural canopy and help cool urban centers. It’s an effort taking place across the country, even in the perhaps unlikely desert metropolis of Phoenix. There, Forestry Supervisor Richard Adkins is promoting an ambitious plan to cover a quarter of the city with tree canopy, a huge undertaking in an area considered a poster child for the detriments of sprawl (and one that, according to a report from Climate Central, is one of the fastest-warming in the country).

"Phoenix is going to continue to grow," says Adkins. "In order to develop sustainably, we need green infrastructure in place. It can’t just be gray. The health, environmental, and educational benefits have been proven by multiple studies."

Phoenix Tree Plan
The Tree and Shade Master Plan in Phoenix seeks to cover a quarter of the city with tree canopy by 2030.
City of Phoenix

Adkins’ Tree and Shade Master Plan, may read like a fantasy to those with a stereotypical view of Phoenix: by 2030, the city will double the amount of tree canopy, including massive planting programs and "engineered shade" underneath "metal trees." But in many ways, the future Askins envisions is merely returning the region to its past. Once criss-crossed with irrigation channels, due to its early agricultural industry, Phoenix was known as the "city of gardens." Before asphalt and development amplified the heat island effect, rows of trees provided a natural means of lowering the temperature.

After a decade in Phoenix, Adkins’s has achieved substantial buy-in from the mayor and local government, mostly due to the numerous benefits of proper urban forestry.  From absorbing water runoff (a big issue during flash floods in the dry desert) to cooling the ground and making it more comfortable to be outside, reducing trips in cars, planting can play a huge role. To showcase the ancillary health benefits and underline the value of green infrastructure, Adkins has taken to occasionally attaching price tags to some of the city’s trees showcasing the values of these plants (Adkins’ research show that for every dollar spent on urban forestry, the city reaps $2.23 in benefits).

He believes it can be a model for more than just Phoenix.

"I see it as a matter of lifestyle and the health of the community more than anything," he says.

This back-to-nature approach is the lynchpin of many major climate plans in cities across the globe. In Berlin, planners want to create "sponge cities" and encourage the construction of more green roofs and urban wetlands, anything to add more plants and restore natural water flow, which prevents rapid evaporation and mediates heat gain.

Other design professionals been incorporating and experimenting with ways to alter building designs to promote natural cooling and energy efficiency.  Architects continue to push new advances in thermal massing, shading, strategic lighting and insulation to cut energy bills. Some engineers have even suggested harnessing the heat, using pipes embedded in roadways to heat water while cooling the surface.

Most striking, however, are the increasing ways architects are incorporating natural features into new building designs. New building standards and research projects, from LEED to the Building Efficiency Accelerator, are promoting improved energy efficiency. Numerous projects, from Stefano Boeri’s acclaimed Bosco Verticale, the Milanese high-rises with vertical gardens, to the inclusion of a sky garden on the supertall Shanghai Tower, a new generation of buildings includes plants, green space, and even parks as more than simply nice amenities. The shading and cooling effects of grafting plants and adding trees can add up for tall towers with higher heating and cooling bills.

oasia singapoer

One of the most striking examples of this Singapore’s OASIA, a recently completed 30-story structure that features exterior walls as trellises. Designed by WOHA, the building, which will eventually be wrapped in green when plants finish growing along the exterior, will benefit from natural cooling and cross-ventilation, with a blooming exoskeleton significantly cutting cooling costs compared to other towers in the tropical city-state. The team hasn’t done exact calculations about exact energy savings, but believes they’ll be substantial. And, as WOHA cofounder Richard Hassell told Curbed earlier this year, restoring a bit of natural balance to an artificial city center has its aesthetic, as well as environmental, payoff.

"Examining the central business districts of so many cities is like looking at the moon from the Earth; one is filled with life, the other is just this collection of dead stone," he says. "With Oasia, we’ve seen so many birds and insects flying around the building. People respond so well to seeing a hummingbird flying right outside their office window."