Our Cities Are Getting Too Hot. Here's What We Can Do

Research InsightsStrategies & Solutions
Written By Marcos Reynaga
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Insights from the Center for Active Design Experts

It’s Hot, and It’s Only Getting Hotter.

For the past few summers, headlines have screamed “highest temperatures on record” or “worst heat wave in history” — and this summer, we’ve already topped them all. Summer has always been a time to get outside and connect with nature, but climate change has made warm months unbearable in some places. While heat can be oppressive in any region, urban heat island effect can intensify the impact of rising temperatures. Cities become hotspots due to the dense concentration of concrete, buildings, and other surfaces that retain heat rather than reflecting and re-emitting it. As we adapt to living in hotter temperatures, there are a number of ways we can cool our communities on small and large scales. Implementing these environmental changes supports both environmental health and human health, as higher temperatures have detrimental effects on our social, mental, and physical wellbeing.

Image: Graph of daily temperature for each year since 1979, world average. Source: Climate Reanalyzer

"While human behaviors (such as choice of location and types of clothing worn) influence the short term impacts of heat on health, the decisions made by architects, landscape architects, and urban planners have substantial long term impacts on human health in hot climates and during heat waves.”

— Andy Dannenberg, Research Advisor, Center for Active Design; Affiliate Professor, Urban Design & Planning, University of Washington

Heat Can Hurt.

When we consider the dangerous and deadly consequences of climate change, category five hurricanes might come to mind, but the truth is that heat is the leading weather-related cause of death in the U.S. Other physical consequences of heat range from dehydration and sunburn to heat exhaustion and stroke, and for anyone with pre-existing cardiac or respiratory conditions, the impacts can be even more severe. Extreme heat also takes a serious toll on mental health as it can affect irritability, memory, attention, and sleep cycles. It  also has been linked to increased rates of emergency department visits for mental health-related conditions, and assaults have been shown to increase by 10 percent at high temperatures. The 1995 Chicago heat wave exemplifies how social connection, or isolation, can exacerbate heat-related health outcomes. Yet while these consequences are severe and compounding, there are a number of ways we can help to cool our neighborhoods and cities to make the warmer months more livable and enjoyable.

Kilroy Art Collection, Los Angeles, California. Architect: Kilroy Realty. ©2015 Lawrence Anderson Photography, Inc.  

Go Green to Get Cool. 

Summertime urban green spaces provide for play, connection, and socializing opportunities. Apart from all of the benefits that green spaces offer for our mental health (see our May blog post), parks can serve as a powerful cooler amidst higher temperatures. Natural or living surfaces (e.g. grasses, mosses, shrubbery, and other forms of landscaping) help cool local air temperatures, and parks can have expansive cooling effects for their whole neighborhood. This effect is known as “Park Cool Island” or “Green Cool Island”, whereby the cooling capacity of an efficiently designed park extends to surrounding areas. When hot air rises, it creates a pressure difference which generates a cycling of air whereby the “cool island” air can spread throughout nearby areas. Research shows that parks can reduce local temperatures by about 4 degrees Celsius in the summer. 

Smaller scale greening initiatives can also make a big difference. Planting trees, installing rooftop gardens or green walls all help to cool urban spaces by shading building surfaces and sidewalks and deflecting sunlight. Evidence suggests that effective tree coverage around buildings can reduce air conditioning needs by 30%, and street trees can not only cool our sidewalks but also ease some of the mental and physical impacts of heat for daily commuters. Even landscaping on a smaller scale can have a big impact on temperatures, especially when utilizing native species; early insights suggest even one additional native plant species can decrease temperatures by about 0.3 degrees.

The Windward, Lake Oswego, Oregon. Photo Courtesy of BentallGreenOak and Chuck Collier Schmidt.

Cool Construction.

Although buildings and urban density directly contribute to urban heat, there are a number of decisions in the construction process that can help to reduce the heat absorption qualities of buildings. Developers can help reduce energy consumption and associated costs by utilizing heat-resistant construction materials, which naturally cool buildings. Similarly, the use and installation of higher albedo surfaces (ones that reflect more sunlight such as sand, snow, or light colored stone and concrete) can also reduce the heat absorption of buildings. For sidewalks and walkways, where tree planting isn’t possible, other construction strategies such as colonnades, cantilever, or paneled structures can support cooling and sidewalk walkability. Even painting concrete surfaces white, a cost-effective strategy to reduce the heat absorption and help lower extreme temperatures by up to 2 or 3 degrees Celsius.

The Ripple Effects of Heat Waves.

Aside from the human health impacts of heat waves and excessive temperatures, heat has severe impacts on the environment — some of which have been acutely felt across North America during recent summers. Most prominently, high temperatures can dry out soil and vegetation, fueling more frequent and powerful wildfires.

As if the physical destruction wasn’t enough, wildfires have far-reaching effects on air quality. For example, in the wake of the wildfire in Canada this summer, smog blanketed New York City and reached as far as the Midwest. Poor outdoor air quality can have severe health consequences. Even short-term exposure to wildfire smoke can trigger headaches and fatigue, while long-term exposure has been linked to reduced student test scores, increased odds of common mental health disorders, and increased risk of respiratory infection. These impacts are felt even more prominently among vulnerable populations, as communities of color are disproportionately exposed to higher levels of air pollution, and those with pre-existing respiratory conditions are at increased risk of hospitalization. As heat and its consequences continue to impact our lives, we must adapt our environments to these new climates.

Adapting for Survival Together.

To continue to live and breathe in our cities safely, we must adapt to the rising temperatures and their consequences. Large-scale interventions, such as developers and city planners using heat-resistant construction materials and designating more space for urban parks, as well as small-scale changes like planting more trees and installing green roofs can all have a significant impact on cooling our cities. Furthermore, outdoor green spaces offer an opportunity for social connection and play, which are important for supporting our social and mental health as well as enjoying the summer months. 

While many larger-scale interventions require the involvement of planners, developers, and government officials, there are several things all of us can do to reduce the temperature in our neighborhoods. Maintaining our local parks and greening our front walkways, walls, and roofs can all help to reduce local surface temperatures and make the summer heat more manageable, fun, and healthy for all. 

560 Mission, San Francisco, California. Photo Courtesy of CommonWealth Partners.

To learn about related heat-combating strategies as part of the new v3 Fitwel Standard coming in December 2023, visit the Fitwel Help Center. Click here to see an overview of how Fitwel works to mitigate heat island effect.

Article contributed by Grace Dickinson, MPH, MUP, Fitwel Ambassador, Associate, Applied Research, the Center for Active Design

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