An official website of the United States government.

We've made some changes to EPA.gov. If the information you are looking for is not here, you may be able to find it on the EPA Web Archive or the January 19, 2017 Web Snapshot.

Heat Islands

Heat Island Newsroom

Two men and one woman in a park with trees read from a clipboardWelcome to EPA's Heat Island Newsroom, which includes recent issues of the Heat Island Newsletter and other notable news items. Older newsletters can be found in the Newsroom Archive. To receive the newsletter and notices of heat island-related conferences by email, sign up for EPA's Heat Island Newsletter.

Note: Some of the following links exit the site. Exit

April 24, 2020 Newsletter

General Heat Islands

  • Houston, TX Resilience Framework Aims to Cool Neighborhoods Houston, TexasIn response to Hurricane Harvey in 2017 and other recent natural disasters, in February, Houston put forward its newly developed Resilient Houston framework. Designed with the 100 Resilient Cities initiative, Shell, and many community stakeholders, the framework aims to build the resilience of Houston’s neighborhoods, especially historically marginalized communities. Resilient Houston is making heat islands a priority with an action and associated steps targeted to “make Houston neighborhoods greener and cooler to combat extreme heat” through a citizen science heat mapping campaign, accelerated tree planting and prairie restoration, expanded green and cool roofs incentives and mandates, piloting cool pavements, and developing innovative shade structures.
  • Coast-to-Coast Heat Island Map Available Online The Trust for Public Land (TPL) and Descartes Labs released a new heat island map based on satellite imagery and other geospatial data to identify heat severity across 14,000 U.S. cities. The map was created using novel data analysis techniques that sped up data processing and greatly expanded the geographic scope from previous efforts. Severity is measured on a scale of 1 to 5, with 1 being a relatively mild heat area and 5 being a severe heat area. TPL believes that knowing where high heat areas are located can help local governments plan and implement cooling strategies.

Resources for Educators

Are you among the many educators and parents that find themselves in need of new lessons and activities to keep young learners engaged? Just for you, the Heat Island Reduction Program pulled together this set of scientific lessons and activities. If you know of other heat island-related learning resources, please share them using our online form. We may feature a growing list of resources in the future.

Cool Materials

  • Somerville, MA’s New Ordinance Cools Things Down Somerville’s zoning ordinance establishes mandates for new construction that aim to cool the local heat island. Roofs and parking areas must meet minimum Solar Reflectance Index requirements. Residential and commercial developments must also meet a minimum sustainability performance standard, or “Green Score.” Buildings can achieve a higher Green Score by taking steps to reduce heat islands, manage stormwater, improve air quality, and sequester carbon. Allowable steps include green roofs, vegetated walls, and other greening strategies. The same zoning update includes new parking regulations that set a maximum number of parking spots developers can build as opposed to a minimum number of spots.
  • Growing Potential of Passive Cooling Technology In 2014, Stanford University researchers created a material that stayed cooler than its surroundings in direct sunlight. Since then, several other teams of researchers have used this technology, known as passive radiative cooling, to test new materials such as paints, plastics, and wood. These materials absorb wavelengths and then emit the radiation through the atmosphere and into space. These “super-cool” materials can lower temperatures by a maximum of 18°F in hot, dry regions. Various super-cool technologies are currently being piloted, which hold the potential to lessen the energy demand of refrigerators and air conditioners, and reduce electricity bills.

Equity

  • Documentary Profiles 1995 Heatwave in Chicago, IL Chicago, IllinoisThe documentary film, Cooked: Survival by Zipcode, tells the story of Chicago’s 1995 heatwave, the most tragic in U.S. history. During the event, humidity and a layer of pollution warmed the city’s heat index to more than 126°F. Over the course of one week, more than 700 Chicago residents died, most of whom were poor, elderly, and African American. This documentary profiles how the legacy and lessons of the 1995 heat wave can inform city planners and managers 25 years later.
  • Historical Housing Policies Spurred Inequitable Exposure to Urban Heat Researchers from Portland State University and Virginia Commonwealth University explored how past “redlining” practices excluded certain neighborhoods from access to home loans or insurance on the premise of race, and now experience disproportionately warmer summertime temperatures. Across 108 urban areas in the United States, 94% of formerly redlined regions displayed land surface temperature differences as high as 13°F compared to non-redlined regions. The study authors attribute these differences to a higher prevalence of impervious surfaces, a lower prevalence of tree canopy and green spaces, and land-use development patterns. These differences were most apparent in southeastern and western U.S. cities.

Public Health

  • Built Environment Can Reduce Urban Heat and Save Lives Researchers from the Georgia Institute of Technology, the University of Texas at Austin, and the California Department of Public Health explored strategies to mitigate urban heat and heat-related deaths in Louisville, KY. They modeled the effects of urban greening, cool roofing and paving, and building and vehicle waste heat reduction strategies. A combination of management strategies decreased summertime temperatures by as much as 10°F and reduced heat island mortality by 22%. These climate adaptation strategies, coupled with existing heat wave protocols such as early warning systems and cooling centers, have the potential to combat future extreme heat and safeguard public health.
  • Video: Improving Health with Greening The Green Heart Louisville, KY initiative is a project spearheaded by the University of Louisville and sponsored by the National Institutes of Health and The Nature Conservancy. Medical researchers are measuring the impact of trees and green spaces on residents’ health. Uneven tree canopy coverage in Louisville contributes to unequal heat impacts, with some areas of the city as much as 10°F warmer. Wealthier neighborhoods have up to twice as many trees as lower-income neighborhoods. The findings of Green Heart Louisville will help inform future efforts to plant trees, especially in low-income neighborhoods that disproportionately experience heat exposure.

Trees and Vegetation

  • Myriad of Ways to Benefit from Urban Forests Urban forests provide a host of benefits including slowing stormwater runoff, cooling air temperatures, dampening noise, and improving public health. Some local governments are getting creative with how to fund their urban forestry efforts. The City Forest Credits program links private organizations looking to buy carbon offsets with companies, governments, and other stakeholders who want to plant trees. The private sector can then fund the projects in return for offset credits. Baltimore, MD is making use of trees that must be cut down by selling logs to mills and producing lumber. Sacramento, CA is using trees to cool the city and reduce energy consumption; the city’s tree canopy can be 20°F cooler than areas with no shade.

January 27, 2020 Newsletter

EPA Updates

Heat Islands and Equity PageThe new U.S. EPA Heat Island Reduction Program web page, Heat Islands and Equity, describes the connection between urban heat and equity; steps for local governments to address heat equity and support at-risk residents; and examples of how New York City, NY, Richmond, VA, and Tucson, AZ are meeting the needs of residents. The new Heat Islands and Equity web page covers:

  • What is heat equity?
  • What is the heat and equity connection?
  • How can heat equity be addressed?
  • What are local governments doing?

General Heat Islands

  • Living With Heat in Boston, MA – The Urban Land Institute (ULI) Boston/New England published a report identifying solutions to mitigate rising temperatures in four areas of the city: East Boston, Lower Roxbury, Chelsea/Everett, and Somerville. ULI teams conducted workshops, interviews, and brainstorming sessions with government, nonprofit, community, and advocacy group stakeholders. Across these four areas, recommendations aligned on the need for a network of cooling stations and/or shaded open-air corridors to facilitate travel during extreme heat. Heat island mitigation strategies included increasing vegetation along city streets, minimizing asphalt and other heat-absorbing surfaces, promoting the use of cool roofs, increasing the use of green roofs or rooftop gardens, and encouraging vegetated facades.
  • Studying Heat Islands in Maryland and Kentucky Public Schools – Teachers in Washington County, MD and Louisville, KY are integrating heat island studies into their curricula. Schools in Washington County are using the Schoolyard Urban Heat Studies Program, which was designed by the Center for Coastal and Watershed Studies at Hood College. This program focuses on environmental and human health impacts of heat islands. Students are measuring surface, water, and air temperatures in areas adjacent to their schools; and using the results to think of ways to mitigate their local heat island. In conjunction with the Partnership for a Green City in Louisville, students are conducting parallel projects to collect heat island data from one urban and one rural school campus. Students on the urban campus measured temperatures of their parking lots, which are divided among three surfaces: white painted asphalt, typical asphalt, and dark asphalt. The students will use these data to inform the best surface color to paint the school’s lots.
  • As Cities Warm, What Role Do Utilities Play? – Missouri’s Office of Public Counsel is urging Kansas City’s local utility to focus a portion of its new energy efficiency proposal on addressing the city’s heat island. The office is suggesting the Missouri Energy Efficiency Investment Act as an avenue to incentivize strategies with both heat island mitigation and energy efficiency benefits, such as cool roofs and tree planting. Under the scheme, the utility would secure financing to pilot beneficial strategies and, in return, the state would match a percentage of the financing raised to give to the utility. These strategies could help decrease customers’ cooling bills and reduce the need for costly energy at peak times.
  • Detailed Heat Action Planning Guide for Greater Phoenix – The Nature Conservancy Arizona, Arizona State University, the Maricopa County Department of Public Health, and other partners recently released a heat action guide for areas within the Phoenix, AZ region. The guide focuses on neighborhoods with some of the highest land surface temperatures, and lowest vegetation cover and greenness in central Maricopa County. The research team worked directly with community members to identify challenges they face and prioritize near-term actions to mitigate and adapt to future heat. To the extent possible, the actions align with other regional efforts to alleviate heat, create climate-resilient cities, and improve public health and safety. Specific cooling strategies include revitalizing vacant lots with trees and vegetation, and increasing shade along transit routes and at bus stops.

Cool Materials

  • Cool Surfaces Could Reduce Heat Island Intensity – A team of researchers from the University of Illinois developed a model to investigate the relationship among wind, urban canyons, and cool surfaces on Chicago, IL’s heat island intensity. The results showed that heat island intensity varied with location and wind direction, and cool surfaces could reduce average heat island intensity. The research also found that a reduction in heat island intensity was correlated with the configuration of urban canyons: heat island intensity varied by as much as 0.2°C (0.4°F) in different urban canyons for the same cool surface type, as a result of wind direction relative to the canyon’s location.
  • Los Angeles (LA) Launches Program for Cool Transit Corridors – LA, CA’s Bureau of Street Services, is leading the Cool Streets LA program to mitigate heat in the hottest and most vulnerable neighborhoods of the city where residents are more dependent on public transportation. Cool Streets LA projects focus on increasing trees and vegetation, cool pavements, light-reflecting roofs, and shaded bus stops. The program aims to complete 6 projects by 2021 and 10 by 2025. Cool Streets LA fits into other local planning efforts, including efforts to reduce the temperature difference between LA’s urban and rural areas by three degrees, and to introduce “cooling features” to every high-frequency transit stop in the city.

Equity

  • The Relationship between Heat and Income in Global Cities – Researchers from Yale University and Arizona State University released research detailing that in 72% of the 25 cities studied worldwide, low-income, intra-city populations experienced disproportionately higher exposure to urban heat. The highest levels of urban heat inequity were located in countries such as Brazil, the United States, and South Africa, which have high-income segregation within their cities. To conduct the study, researchers combined satellite observations with census data to evaluate the relationship between heat islands and income at the neighborhood scale. The strongest contributor of intra-urban heat island variability among the physical characteristics considered in the study was the neighborhood’s vegetation density.
  • Equitable Access to Green Roofs in Detroit – DetroitStudents and researchers at the University of Michigan investigated the relationship between low-income and marginalized residents and their access to green roofs in Detroit, MI. By evaluating spatial and demographic data, researchers found that low-income residents are within walking distance of Detroit’s cooling centers, but green roofs are located in the predominantly White and affluent parts of Detroit. This analysis and thesis can be used to site future green roofs near Detroit’s heat-vulnerable neighborhoods.
  • Scoping Sacramento’s Urban Heat Island – Researchers at the University of California, Davis, are exploring Sacramento, CA’s hotter future. They believe the city’s heat islands occur in its least-affluent neighborhoods, which have fewer trees and higher rates of asthma, obesity, and diabetes. Several regional partners are working to address these disparities. The Sacramento Metropolitan Utility District is partnering with the Sacramento Tree Foundation to offer cost-free trees and planting guidance to residents, schools, churches, and businesses. Moreover, the Sacramento Metropolitan Air Quality Management District enlisted the support of an atmospheric modeler and has a preliminary map of the city’s heat island. The city will update its Urban Forest Master Plan in 2020. 

Green Roofs

  • Green Roof Regulations, Incentives, and Best Practices – Green Roofs for Healthy Cities’ latest Green Roof and Wall Policy in North America report profiles a number of principles for establishing effective policies, including understanding the local value added and cost of green roofs, establishing markets through regulation, and encouraging green roofs via incentive programs. It also highlights several lessons learned for policymakers, including conducting transparent cost-benefit analyses; consulting with stakeholders; and supporting professional green roof training such as best practices in design, installation, and maintenance.
  • Lessons from a Decade of Green Roofs in Toronto, ON – Toronto’s decades old Green Roof By-Law and Eco-Roof Incentive Program align with the city’s evolving policy objectives, including heat island mitigation, stormwater management, climate change mitigation, energy efficiency, air quality improvement, environmental conservation and restoration, and job creation. These initiatives boast multiple achievements, including 620 mandated green roof projects with 500,000 square meters of planned or completed green roofs, 426 voluntary eco roofs (cool and green) covering nearly 800,000 square meters, 58 million gallons of retained stormwater, and 3.2 million kWh of annual electricity savings.
  • Green Roof Policies Grow – Green roofs provide a host of benefits, including lowering the surrounding air temperature, filtering stormwater, reducing energy use, and serving as a respite for city residents. Cities across the United States recognize these benefits and have created green roof incentive programs or requirements. In 2016, San Francisco, CA began requiring that 15–30% of roof space on new buildings include solar panels or green roofs. More recently, New York City, NY passed a requirement for green roofs or solar panels on new construction. Washington, DC and Philadelphia, PA each offer green roof tax credits.

October 17, 2019 Newsletter

EPA Updates

Spruce Up! Using Green Roofs and Green Spaces to Beat the Heat – In case you missed it, webcast materials including a recording, slides, transcript, and questions and answers are now posted for the 90-minute webcast focused on how green roofs and other green spaces are being used to address urban heat across the country. The webinar highlighted the variety of benefits that such practices can bring, how green roofs improve air quality and public health in Kansas City, and Denver's recent green building ordinance.

General Heat Islands

  • Excessive Heat PosterSocial Media Downloadables on Heat Islands and Heat Safety  – With record-breaking temperatures extending into autumn, it is not too late to get the word out about the effects of heat islands and extreme heat. The National Weather Service developed 18 scripted social media messages and freely available graphics. The Tweets, Facebook posts, and graphics explain how the urban environment contributes to the heat islands effect even after the sun goes down; and other heat safety messages for outdoor workers, children, and pets.
  • New Satellite Data a Step Closer to Mapping by Block-Level  – The United States Geological Survey Earth Resources Observation and Science Center’s satellite data are becoming increasingly sophisticated and automated, making it easier and less costly to identify hot spots on a block-by-block basis. Using Atlanta, GA, as a pilot, researchers are using the Landsat Analysis Ready Data surface temperature stream to measure the heat island effect with more than 30 years of annual average temperatures for each 30-meter plot. The goal is to replicate these same monitoring capabilities across the U.S. Such satellite data are important to further understand the relationship between hot areas and vulnerable populations, which can inform future policy.
  • Heat Island Mitigation Modeling in the Kansas City region   – Lawrence Berkeley National Laboratory partnered with the Kansas City region’s planning organization, the Mid-America Regional Council, to identify costs and benefits of heat island mitigation measures. This comprehensive report investigates the impacts of cool roofs and planting trees, and improving irrigation with vegetation. Across a range of past summer heat wave events, the exercise found benefits from the practices, including near-ground temperature reductions, direct and indirect electricity savings, cost savings, and emissions reductions.
  • Video! Using Multiple Methods to Map the Heat Island in Athens, GA – Science Nation released a four-minute video chronicling recent research from students and faculty at the University of Georgia to map Athens, GA’s, heat island. Temperature data are being collected by both buses and wearable sensors. The local data are then used to create and display fine-resolution, hyperlocal maps. This project builds on recent trends relying on student or citizen science as a vital component of mapping and understanding heat islands.
  • Student Satellite to Capture Urban Thermal Images   – In 2020, over 100 science and engineering students, faculty, and researchers at Arizona State University will launch a low-orbit satellite named “Phoenix.” Over the course of a two-year mission, Phoenix will take daytime and nighttime thermal images of several U.S. cities. The students will interpret the heat radiation images to better understand the cities’ heat islands. Phoenix, AZ, was chosen as the first target city as its developed land area is increasing at a rate faster than most cities, contributing to the city’s heat island.
  • Rethinking Urban Dynamics in the Face of Heat Extremes  – A recently authored journal article by researchers from Lawrence Berkeley National Laboratory used California as a test case to examine how extreme heat events, population growth, and heat island mitigation measures will interact and impact cities in the future. The work considers how heat islands will exacerbate extreme heat events, and how mitigation actions can reduce heat exposure and warming. The researchers found that implementing cool roofs can offset 51–100% of increased heat exposure in urban regions, underscoring the importance of this strategy for mitigating the heat island effect.

>Equity

  • Baltimore MDEight-Part Series Unpacks the Toll of Heat Inequality in Baltimore, MD – The Howard Center for Investigative Journalism, the Capital News Service, National Public Radio, and other partners teamed this past summer to investigate the effects of rising temperatures on public health in Baltimore, MD. The eight articles reveal information from interviews with residents, emergency room doctors, public health leaders, city and state officials, climate scientists, urban foresters, tree-planting crews, and church leaders. The series depicts how the effects of heat islands are intertwined with themes of social and environmental justice.
  • Building Neighborhood Resilience in Philadelphia, PA – The Philadelphia Heat Vulnerability Index found neighborhoods that are the hottest are also where residents may be most vulnerable to extreme heat. In response, the Philadelphia Office of Sustainability developed a neighborhood plan to build the resilience of Hunting Park, which can run 22°F warmer than other parts of the city. The Office of Sustainability engaged in an 8-month process that included dozens of events and workshops, which reached 600 residents, and a survey completed by 530 residents to evaluate the heat impacts. The plan’s recommendations include the potential for a heat relief network; and heat island mitigation measures such as increasing the number of trees, green spaces, and cool roofs throughout Hunting Park. 

Cool Materials

  • Energy Benefits of Cool Walls in Hot Climates – The Heat Island Group at Lawrence Berkeley National Laboratory investigated the potential benefits associated with cool walls on residential and commercial buildings. The researchers used the building energy simulation program EnergyPlus to perform over 100,000 simulations throughout the U.S. The study found that cool walls result in source energy reduction, energy cost savings, and emissions reductions. In California, the air-conditioning cost savings were 4.0–27.0% in homes, 0.5–3.8% in office buildings, and 0.0–8.5% in retail stores. In other warm climate zones, energy cost savings were 1.8–8.3% in homes, 0.3–4.6% in office buildings, and 0.5–11% in retail stores.
  • Reflective Walls, Roofs, and Pavements Could Cool Gilbert, AZ  – A team of researchers from the University of Illinois and other institutions authored an article demonstrating how cool surfaces affect the heat island in an individual suburban development in Gilbert, AZ. These surface types include new asphalt concrete, typical concrete, and reflective concrete pavement; reflective roofs and walls only; and reflective pavements, roofs, and walls. Under the study conditions, the researchers found that changing all walls, roofs, and pavements to reflective surfaces was the most effective strategy. These conclusions highlight the importance of engaging homeowners in adopting heat island cooling solutions.
  • Heat Island Resource Highlight – Keeping Your Cool Fact SheetCheck out the Heat Island Reduction Program’s fact sheet Keeping Your Cool: How Communities Can Reduce the Heat Island Effect. This four-page fact sheet gives an overview of what heat islands are, how they affect us, highlights strategies to reduce heat islands, and explains the benefits of mitigating heat islands. This resource is a useful primer to introduce and share information with those new to the topic of heat islands. 

Building Resilience

  • Scorched: Extreme Heat and Real Estate – A report released by the Urban Land Institute considers the role of U.S. real estate developers, designers, and policy-makers to mitigate the effects of extreme heat on people and infrastructure, especially in urban environments. Solutions focus on improving the built environment and outdoor spaces to be adaptable to environmental conditions through innovative design approaches, technologies, and policies. Strategies such as improving the form and layout of our cities, using heat-resistant construction materials, and increasing vegetative cover have the potential to mitigate the effects of heat islands. The report features case studies on Cincinnati, OH; New York, NY; Toronto, ON; and Los Angeles, CA.
  • Passive Building Design Elements Could Alleviate Heat Disasters – Researchers from Arizona State University and the National Center for Atmospheric Research simulated the effects of heat on residential buildings in the absence of cooling systems. Their investigation considered that roughly 50 million residents living in cities are at significant risk of a “heat disaster,” which consists of a power outage or air conditioning loss during a hot weather episode. To mitigate effects of a heat disaster, the researchers identified passive building design techniques (e.g., shading, reflective surfaces, ventilation) as options to enhance the performance of buildings. The researchers suggest that thermal resiliency be considered in developing building codes.

Public Health

  • Boy Drinking WaterKiller Heat in the United States – A new Union of Concerned Scientists report investigated how extreme heat events will likely affect the U.S. population and public health in the coming decades. In particular, heat may be a growing health concern for some individuals more than others, such as children, older adults, and outdoor workers. The report authors recommend heat-smart infrastructure actions, including urban forestry, passive cooling, shading and trees, and cool roofs that have heat island reduction benefits.
  • Exposure to Trees Promotes Good Mental Health – Research from the University of Wollongong in Australia reveals the importance of protecting and restoring the urban tree canopy to promote mental health wellbeing. Of nearly 50,000 adults over the age of 45, the availability of tree canopy coverage greater than 30% within a one-mile range was associated with 31% lower odds of psychological distress after adjusting for age, sex, income, economic status, relationship status, and educational level. The same results did not hold true for lower levels of tree canopy coverage or exposure to grass. The study authors suggest street trees as one method to reduce temperatures and improve mental wellbeing.

Trees and Vegetation

  • New Guide on Urban Tree Canopy Assessment – The U.S. Forest Service released an Urban Tree Canopy Assessment guide that helps users follow a five-step process: (1) planning, (2) assessment, (3) analysis, (4) implementation, and (5) monitoring and evaluation. The assessment generates critical information for setting local tree canopy goals and priorities. The assessment framework can be combined with other data sources to help communities make policy decisions that optimize benefits such as heat island mitigation.

July 8, 2019 Newsletter

EPA Updates

  • Spruce Up! Using Green Roofs and Green Spaces to Beat the Heat  Join this 90-minute webinar to learn how green roofs and other green spaces are being used to address urban heat across the country. The webinar will highlight the many benefits that such practices can bring, such as how green roofs are improving air quality and public health in Kansas City, Missouri. The event will also feature a national green roof expert and delve into Denver, Colorado's recent green building ordinance.
    • Overview of Heat Islands and EPA’s Heat Island Reduction Program. Victoria Ludwig, U.S. EPA Heat Island Reduction Program.

    • Green Roofs and Walls: Strategies for Fighting the Urban Heat Island. Steve Peck, Green Roofs for Healthy Cities.

    • Environmental Effects of Green Roofs, a Case Study in Kansas City. Robyn DeYoung, U.S. EPA.

    • Denver’s Green Building Ordinance Development Process. Katrina Managan, Denver Department of Public Health and Environment.

        Register for the Webcast

General Heat Islands

  • Listen Now! Science Friday Features Heat Islands! – The long-running Science Friday public radio program unpacked the topic of heat islands in a recent episode. The episode features speakers from the Lawrence Berkeley National Laboratory and the Global Cool Cities Alliance, among others. It delved into what communitites across the United Stats are doing to understand and mitigate heat islands. Add it to your podcast queue!
  • How Surface Characteristics Contribute to Heat Islands –  In a recent journal article published in Urban Forestry & Urban Greening, researchers looked at the city-scale (versus the local-scale within a city) effects of greenspace to mitigate surface heat island intensity. Using the Illinois, Indiana, and Ohio region as a test case, they found that the largest determinant of the surface heat island was urban and rural differences in characteristics such as the vegetation index. To a lesser extent, greenspace spatial pattern and then urban form determined urban surface heat island intensity.
  • Bird's eye view of a gridlike city with tree-lined streetsStrategies to Improve Comfort of Outdoor Urban Spaces – In Science of The Total Environment, researchers from multiple institutions recently compared the effectiveness of changing the urban geometry, planting vegetation, using cool surfaces, and incorporating water bodies to reduce air temperature and improve the thermal comfort of urban outdoor spaces. While all the strategies provided some level of comfort, changes in urban geometry generated the greatest improvement, particularly in hotter and drier climates.
  • Heat Islands Attributed to Evaporative Capacity (or Lack Therof) – Looking across 60 cities in North America, researchers from several universities and institutions investigated daytime surface heat island intensity – the difference between urban surface temperatures and surface temperatures in surrounding rural areas (rather than air temperatures). They found that daytime surface heat island intensity is most attributable to the capacity of urban and rural areas to evaporate water as opposed to an area’s efficiency to convect heat into the atmosphere. This research underscores the potential of green infrastructure to mitigate the heat island effect.

Cool Roofs

  • The City of Buffalo, New YorkBuffalo Cool Roof Project Earns City's Civic Innovation Eco Challenge PrizeTwo Buffalo residents recently earned a Civic Innovation and Eco Challenge award from the city. The residents created the Buffalo Cool Roof Project using geographic information system mapping and artificial intelligence to identify which roofs are the best candidates for conversion to cool roofs. Property owners can even see if their own roof is a good candidate. The Civic Innovation and Eco Challenge aligns with Buffalo’s overall goal to become designated as a Climate Smart City by the New York State Energy Research and Development Authority.
  • How do Energy Savings Shift as Cool Roofs Age? Students and professors from New Mexico State University explored how energy savings from cool roofs may change as they age and lose reflectance. Even when considering a drop in solar reflectance, cool roofs provided a small, yet noticeable, improvement in energy savings for all states considered in the study. Results suggested that cool roofs combined with insulation are the best solution to prevent energy transfer into buildings.

Equity

  • Bird's eye view of Missoula, MontanaFrom Montana to New York, Mapping Heat Vulnerability to Protect Community Health – Both Missoula, Montana and the South Bronx, New York are working with the Thriving Earth Exchange to identify local heat islands that could threaten sensitive populations within their communities. In Missoula, community leaders and partners overlaid U.S. Census demographics for sensitive populations with heat exposure at the city block level. The group used the map to inform recommendations for building codes that could alleviate the heat island effect. Efforts in the South Bronx are just gearing up. Their goal is to generate information that can be used to improve the community’s ability to respond to extreme heat, identify areas for mitigation, and inform policy change.

Green Roofs

  • Green Roofs to Top New Buildings in New York City – New legislation, dubbed the “Green Roof Act,” will transform roofs across New York City, New York. New residential and commercial structures, or structures undergoing signification renovation, will need to incorporate plants, solar panels, and/or mini wind turbines on their rooftops. Related legislation includes provisions to improve building energy efficiency for those greater than 25,000 ft2. Green Roofs for Healthy Cities helped to craft and pass the Green Roof Act.

Trees and Vegetation

  • Can Tree Cover Counteract the Effect of Impervious Surfaces? – In recent reports, researchers from the University of Wisconsin and Memorial University of Newfoundland used a bicycle-mounted measurement system to measure air temperature in a spectrum of tree-covered to tree-bare areas in Madison, Wisconsin. Daytime temperatures varied from 1.1 to 5.7°C (2.0–10.3°F), with the coolest areas having greater than 40% canopy coverage. Daytime temperatures increased with increased impervious cover. Nighttime temperatures varied from 1.2 to 3.0°C (2.2–5.4°F), with the highest temperatures associated with impervious surfaces.
  • Present and Future Ecosystem Services of Trees in the Bronx, New York – A research team at the State University of New York and the U.S. Forest Service recently estimated the value of ecosystem services generated by trees, including air pollutant removal, carbon storage and sequestration, urban heat island reduction, stormwater runoff reduction, and other socioeconomic benefits. Using the i-Tree suite, they estimated the value of trees in 2010 and 2030. Combining the benefits of each of these services, the monetary value of trees in the Bronx was estimated at $37.6 million in 2010, and $40.7–$43.9 million in 2030 if the trees grow to maturity.
  • Trees Generate Cooling Effects during Both Heat and Cold Waves – Authors from Arizona State University published a study looking at the effects of urban trees during periods of extreme heat and extreme cold. Using a surface cooling rate measure comprised of land surface temperature and fractional tree cover, results showed that during heat waves trees provide a 1.3°C (2.4°F) cooling effect for each percentage increase in fractional tree cover. During cold waves, trees provide a much smaller 0.02°C (0.04°F) cooling effect for each percentage increase in fractional tree cover.

Public Health

  • Nurse helping an elderly personTree Canopy Cover Can Brighten the Outlook of Nursing Home Residents –  A recently authored journal article from researchers at the University of Illinois and University of Washington examined the relationship between tree canopy cover around 9,186 U.S. nursing homes and residents suffering from depressive symptoms, which encompass clinical depression and milder metal health disorder symptoms. They found that more tree canopy coverage was associated with lower rates of symptoms of depression, suggesting that nursing homes should incorporate greening measures to help residents’ mental health.
  • Trees Can Prevent Thousands of Deaths from Extreme Heat A team from The Nature Conservancy, the National Aeronautics and Space Administration, and Stanford University published an article detailing the relationship among tree cover, air temperatures, associated heat-related mortality and morbidity, and electricity consumption across 97 U.S. cities. Roughly 13% of the corresponding population experiences a temperature reduction benefit of 1.0°C (1.8°F) or higher from trees, while another 25% of the population experiences a temperature reduction benefit of 0.5–1.0°C (0.9–1.8°F) from trees. Across the 97 cities, tree cover avoids 243–346 deaths each year. They estimate the value of avoided mortality, morbidity, and electricity consumption at $1.3–2.9 billion annually.