If You Can’t Take the Heat, Get Into the Street
By Jake Elder, Sustainability, Bloomberg Associates
It is increasingly difficult to avoid references to climate change in the news. With record-shattering heatwaves this summer, people around the world have felt the effects of climate change. UN Secretary General António Guterres said it best:
“…we are on track for the period from 2015 to 2019 to be the five hottest years on record. This year alone, we have seen temperature records shattered from New Delhi to Anchorage, from Paris to Santiago, from Adelaide and to the Arctic Circle.”
In the U.S., July 2019 was the hottest month ever recorded. Anchorage, Alaska saw its first day with temperatures over 90° F. These impacts were felt around the rest of the country: Boston had nearly as many days above 90° F in July as it averages in an entire year, setting a monthly temperature record of its own; similar records were set in Maine, Connecticut, Arizona, and New Mexico.
Heat is a threat to all parts of our planet, but is particularly dangerous for residents of cities. The combination of dense buildings and dark, impermeable surfaces such as streets and parking lots cause urban areas to absorb heat much faster than surrounding, less developed areas. This means that urban areas are up to 5˚ F to 22 ˚ F hotter at night.
Public paved spaces like streets and parking lots account for over a third of the total land area in most cities and play a major role in contributing to the Urban Heat Island (UHI) effect. But these spaces also present an opportunity. Unlike rooftops or existing green spaces, paved surfaces are regularly dug up and resurfaced which provides ongoing opportunities to change their design.
And because these spaces are typically publically-owned they are increasingly becoming a hotbed for innovation. Cities and entrepreneurs around the world have been evaluating these spaces and are seeking to implement “cool pavements” that deliver the same service but also address the UHI. “Cool pavements” come in a variety of forms, from a coating on street surfaces that increases the solar reflectivity to entirely new, permeable concrete that can absorb water, later evaporating and cooling the surrounding area.
To learn more about these innovative solutions, Bloomberg Associates conducted a global scan of “cool pavements” to see how cities are tackling this issue and what products have been developed to meet these needs. Here are three major findings:
1) Test these materials at scale. In one of the first pilots for “cool pavements” in the U.S., the City of Los Angeles found that applying a surface treatment to residential streets lowered surface temperatures by up to 16˚ F. Despite these preliminary results, a number of questions have been raised about scaling this approach. Concerns include the impact of reflective coatings on air temperatures, not just the surfaces they are applied on; the durability of these new technologies; and the environmental impact of their development. Additional testing will help us better understand the impact of using certain materials.
2) Target pedestrian-heavy areas. The research to date suggests that cool materials have a major effect on air temperatures. Furthermore, only 2 of the 13 technologies we evaluated were rated for use in areas with high vehicle traffic. Cities will get the best results when they apply these interventions to areas where people regularly spend time outside, and when they pair cool pavement efforts with other solutions like shading. For example, Paris’ Urban Oasis program brought together cool pavements, permeable surfaces, greenery, and shading efforts to create neighborhood refuges at City schoolyards. The initial three-school pilot was well received; the program was awarded €5M from the EU and is expanding to an additional 30 schoolyards in 2019.
3) Implement a holistic, long term strategy. Cities looking to address the UHI effect should start by identifying the hottest areas of the city that also have the greatest density of pedestrians — particularly vulnerable populations. This exercise can help cities prioritize high-need areas and the most effective solutions. Additionally, cities will see the greatest impact if they incorporate cool pavements into their design specifications for ongoing resurfacing and paving efforts, taking advantage of existing infrastructure updates. For example, in Tokyo, by integrating cool pavements into its overall road maintenance and construction program, the city has been able to improve over 116km of roadways in just a few years.
To learn more about Bloomberg Associates’ findings, download the full report and join a webinar with the C40 Cool Cities Network in September.
