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Keeping Your Cool on a Heat Island

2014 July 21


Jessica on Heat Island

Jessica on Heat Island

By Jessica D’Itri

It’s 9 a.m. and I’m on my way to my internship at EPA. I’m sweating through my clothes, my hair is plastered to my neck, and mascara is pooling under my eyes. The summertime heat and D.C.’s swampy humidity are bad enough, but an extra dose of suffering comes from the heat island effect.

Washington, D.C., like many developed areas, is a heat island: all of the pavement and buildings absorb and retain much more heat than less built up areas. This means they can be 1.8 to 5.4°F warmer on average, and up to 22°F warmer in the evening.



Temperatures climb more among buildings and roads than open land and vegetation.

Temperatures climb more among buildings and roads than open land and vegetation.

Heat islands aren’t only uncomfortable, they can be hazardous to people’s health. And, they can create a vicious cycle: higher city temperatures mean more electricity is needed to cool buildings, which in turn may increase air pollution. Also, when an extreme heat wave hits a city already stressed by the heat island effect, it can increase the risk of heat-related illness and death. This risk is worse for children, the elderly, and the ill, who are more vulnerable to extreme heat and polluted air.

EPA’s Heat Island Reduction Program suggests several strategies that cities can take to reduce summertime heat islands:

  • Planting trees near buildings: Trees and other plants help cool the environment.
  • Installing green roofs: Green roofs provide shade and remove heat from the air.
  • Installing cool roofs: Cool roofs have a high solar reflectance that helps reflect sunlight and heat away from the building.
  • Using cool pavements: Cool pavements reflect more solar energy, enhance water evaporation, or have been otherwise modified to remain cooler than conventional pavements (like those that allow water to permeate below the surface).

These tactics reduce demand for energy to cool buildings, which cuts carbon pollution and lowers bills. Using these cool technologies reduces the heat island effect, helping everyone stay cool.

Permeable pavement reduces runoff, mitigating heat buildup and improving drainage.

Permeable pavement reduces runoff, mitigating heat buildup and improving drainage.


The city heat can be a real nuisance (especially when trying to look professional for work!), but it can also be dangerous. Luckily, there are plenty of things that can be done to combat the heat island effect and keep safe in the heat. Listening in on heat island webinars and calls, I’m excited to hear about how communities are taking action to make life safer and more comfortable for residents. There’s a lot we can do as individuals and communities to reduce heat island, and those efforts can add up and have a big impact for us and the environment.

And there’s some good news for D.C. The District Department for the Environment recently created a Green Building Fund Grant Program, which has several goals, including assessing the health impacts of urban heat islands in this city. So, hopefully, future interns will benefit from this research and resulting policy changes. What is your city doing to reduce the heat island effect?

About the author: Jessica D’Itri is a Master of Public Policy student at the Gerald R. Ford School of Public Policy at the University of Michigan. Prior to attending the Ford School, she served as an environmental educator with Peace Corps Nicaragua. She is interested in learning how communities and local governments can implement policy to best benefit people and the environment.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action, and EPA does not verify the accuracy or science of the contents of the blog.

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One Response leave one →
  1. Jessica Williams permalink
    August 18, 2014

    Great article . Heat Island ! We can seriously feel the heat island effect around are offices and parking lot. And we’ve been considering installing a green roof on the building (which is almost the size of the parking lot) figuring it would at least off set our black top. And I’m sure improve with electric costs month to month. I’m in the process of checking out contractors but if you know of any good ones in the Miami/Key Largo area please let me know:)

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