Major Cities Confront Urban Heat Island Effect

Major Cities Confront Urban Heat Island Effect

A survey of North American cities by the American Council for an Energy Efficient Economy (ACEEE) and the Global Cool Cities Alliance (GCCA) finds that confronting challenges of extreme weather, adapting to a changing climate and improving the health and resiliency of urban populations are driving cities to develop and implement strategies to reduce excess urban heat. Nearly two-thirds of cities surveyed cited local extreme weather events as a key reason for initiating urban heat island mitigation strategies.

“US cities are waking up to the growing threat of urban heat and employing a number of innovative approaches suited to their location and priorities,” says Virginia Hewitt, ACEEE researcher and report author. “Our report will help local planners adapt these practices to even more communities across the country.”

ACEEE and GCCA surveyed 26 cities in the United States and Canada representing all major climate zones, geographies and city sizes. Despite the diversity of the respondents, several common themes emerged. Local governments are “leading by example” by requiring use of “cool” technologies, such as reflective roofs on municipal buildings, lining city streets with shade trees and raising public awareness. Additionally, more than one-half of cities have some kind of requirement for reflective and vegetated roofing for private sector buildings. Almost every city had policies to increase tree canopy and manage stormwater.

“Our report finds that by addressing urban heat islands, cities are more effectively delivering core public health and safety services, thus making them attractive places to live, work and play,” said Kurt Shickman, executive director of the Global Cool Cities Alliance.

The Report includes case studies on how several cities have responded to urban heat, demonstrating the variety of strategies employed. In response to a study noting that Houston’s roofs and pavements can reach 160° F, the city now requires most flat roofs to be reflective. After an extreme heat wave in 2008, Cincinnati lost much of its urban canopy and instituted an aggressive forestry plan. Washington, DC, has instituted a wide suite of programs like Green Alleys, which helps residents manage excess stormwater by replacing pavement with grass and trees, and requiring reflective roofs on new buildings. The survey also found that most city governments are not acting alone to reduce excess heat. States, neighboring jurisdictions, utilities, developers, contractors and local building owners are collaborating to create incentives for communities to reduce urban heat and to mainstream these practices.

“We recognized a number of years ago that keeping New York cooler was an important part of protecting public health and becoming more resilient. We started with cool-roof volunteer programs that raised awareness and understanding while coating 5 million square feet of rooftops. These voluntary efforts led to the cool roof ordinance requiring investments in reflective roofs on certain buildings,” said Wendy Dessy of NYC Service.

Cities surveyed in the report include: Albuquerque, NM; Atlanta, GA; Austin, TX;
Baltimore, MD; Boston, MA; Charlotte, NC; Chicago, IL; Chula Vista, CA; Cincinnati, OH; Dallas, TX; Denver, CO; Houston, TX; Las Vegas, NV; Los Angeles, CA; Louisville, KY; New Orleans, LA; New York, NY; Omaha, NE; Philadelphia, PA; Phoenix, AZ; Portland, OR; Sacramento, CA; St. Louis, MO; Toronto, ON; Vancouver, BC; and Washington, DC.

To view “Cool Policies for Cool Cities: Best Practices for Mitigating Urban Heat Islands in North American Cities,” visit The survey is also available on the Cool Roofs and Pavements Toolkit:

ACEEE acts as a catalyst to advance energy efficiency policies, programs, technologies, investments and behavior. For information about its programs, publications and conferences, visit The Global Cool Cities Alliance is a non-profit organization working with cities, national governments and other stakeholders to advance policies and actions that reduce excess urban heat and mitigate effects of climate change through global cooling.