Nav: Home

How green and cool roofs could impact urban climate

June 01, 2016

A video related to this research can be found here:

More than 50 percent of today's population lives in cities. According to the United Nations Development Programme, that number is predicted to rise to 70 percent by 2050. Growing urbanization increases the overall temperature of a city as buildings, roads, parking lots and other infrastructure absorb heat, creating an urban heat island (UHI). A UHI causes areas like Chicago to be significantly warmer than surrounding rural areas, which threatens urban sustainability and can lead to high mortality rates and scarcity of resources as well as high electricity demands.

Newly published University of Notre Dame research found that the use of roofs with vegetation or reflective surfaces on top of Chicago's current infrastructure could reduce UHI by lowering roof temperatures by a range of 3 to 4 degrees Celsius (5.4 to 7.2 degrees Fahrenheit). The study, part of a collaboration between Notre Dame and the City of Chicago, examined the efficacy of green or cool roofs using a regional climate model to simulate various real-world urban rooftop conditions.

"Our research analyzed how these non-conventional roofing strategies would impact energy use and air quality, as well as to understand the unique role Lake Michigan would play in mitigating UHI in Chicago," said Ashish Sharma, postdoctoral researcher with the Environmental Change Initiative and the Department of Civil and Environmental Engineering and Earth Sciences, who led the study. "The lessons learned from this research will be integral for city planners as they decide how green infrastructure should be implemented."

The researchers looked at the effects of green roofs -- roofs that are at least partially covered with vegetation -- and cool roofs -- roofs that are designed to reflect more sunlight and absorb less. When compared to conventional roofs, both types had significantly lower temperatures. Therefore, by using either green or cool roofs, the temperature of the city could be greatly reduced.

This research builds on a collaboration between the University of Notre Dame, through Harindra Joseph Fernando, Wayne and Diana Murdy Endowed Professor of Civil and Environmental Engineering and Earth Sciences as well as Aerospace and Mechanical Engineering, and the City of Chicago to support the Chicago Wilderness Green Infrastructure Vision plan for 2040.

"Many cities are proactively working to reduce adverse impacts of UHI and this research is an attempt to investigate optimal UHI mitigation strategies, paying particular attention to the City of Chicago, with which we have had long-standing collaboration on urban research," said Fernando. "The main conclusions of this work has policy and planning implications on how the city should respond to a growing UHI issue and what mitigation strategies should be adopted in the face of rapid urbanization and climate variability."

In addition, the research team also evaluated wind patterns from Lake Michigan to understand how reducing UHI could impact wind within Chicago. By using green or cool roofs to reduce the temperature of the city, there will be less pressure difference caused by cool air from the lake mixing with relatively less hot air of Chicago, thus decreasing lake-breeze within the city. These results have revealed additional urban climate research questions. For example, when there is a reduction in lake-breeze and UHI in the city, there is also less vertical mixing of air. Based on current findings, it appears that this could stagnate air near the ground and potentially cause air quality issues.

"The next step in our research is to look at how the chemistry of green roofs might impact our meteorologically based findings," Sharma said. "It is possible that plants may pose a solution for this issue, but competing feedbacks from green and cool roofs for UHI mitigation should be carefully considered."

This summer, Sharma will work with Fei Chen of the Research Applications Laboratory at the National Center for Atmospheric Research to evaluate the role these mitigation strategies play in limiting the potential stagnation of air when implemented and address potential savings in electricity loads.

"This study provided city planners with meaningful and practical guidance regarding the pros and cons of using green roofs and cool roofs to mitigate urban heat inlands and heat stress," Chen said. "I'm looking forward to collaborating with Sharma this summer on applying new urban modeling capabilities developed at NCAR to explore how much energy a city like Chicago can save by using green roofs or cool roofs."
This study was published in Environmental Research Letters. Apart from Sharma, Fernando and Chen, other co-authors include Alan Hamlet, assistant professor of civil and environmental engineering and earth sciences as well as biological sciences; Patrick Conry, graduate student within civil and environmental engineering and earth sciences; and Jessica Hellmann, formerly of Notre Dame and currently the director of the Institute on the Environment and professor of biological sciences at the University of Minnesota. The study is available online at

For more about environmentally focused research at the University of Notre Dame, visit

University of Notre Dame

Related Environmental Engineering Articles:

Re-engineering antibodies for COVID-19
Catholic University of America researcher uses 'in silico' analysis to fast-track passive immunity
Next frontier in bacterial engineering
A new technique overcomes a serious hurdle in the field of bacterial design and engineering.
Does MRI have an environmental impact?
Researchers from Tokyo Metropolitan University have surveyed the amount of gadolinium found in river water in Tokyo.
COVID-19 and the role of tissue engineering
Tissue engineering has a unique set of tools and technologies for developing preventive strategies, diagnostics, and treatments that can play an important role during the ongoing COVID-19 pandemic.
Environmental solutions to go global
New Australian technology that could fix some of the world's biggest environmental pollution problems -- oil spills, mercury pollution and fertiliser runoff -- will soon be available to global markets following the signing of a landmark partnership with Flinders University.
Engineering the meniscus
Damage to the meniscus is common, but there remains an unmet need for improved restorative therapies that can overcome poor healing in the avascular regions.
Artificially engineering the intestine
Short bowel syndrome is a debilitating condition with few treatment options, and these treatments have limited efficacy.
UM environmental engineering faculty publishes paper on risk assessment
The basis behind the newly published dose-response function is that the relationship between intra-cellular responses and multi-organ, multi-cellular governing processes is reflected in the overall dose-response function.
The success of an environmental charge
In October 2015, England introduced a charge for single-use plastic bags in supermarkets.
Next-gen batteries possible with new engineering approach
Dramatically longer-lasting, faster-charging and safer lithium metal batteries may be possible, according to Penn State research, recently published in Nature Energy.
More Environmental Engineering News and Environmental Engineering Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: The Power Of Spaces
How do spaces shape the human experience? In what ways do our rooms, homes, and buildings give us meaning and purpose? This hour, TED speakers explore the power of the spaces we make and inhabit. Guests include architect Michael Murphy, musician David Byrne, artist Es Devlin, and architect Siamak Hariri.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

What If?
There's plenty of speculation about what Donald Trump might do in the wake of the election. Would he dispute the results if he loses? Would he simply refuse to leave office, or even try to use the military to maintain control? Last summer, Rosa Brooks got together a team of experts and political operatives from both sides of the aisle to ask a slightly different question. Rather than arguing about whether he'd do those things, they dug into what exactly would happen if he did. Part war game part choose your own adventure, Rosa's Transition Integrity Project doesn't give us any predictions, and it isn't a referendum on Trump. Instead, it's a deeply illuminating stress test on our laws, our institutions, and on the commitment to democracy written into the constitution. This episode was reported by Bethel Habte, with help from Tracie Hunte, and produced by Bethel Habte. Jeremy Bloom provided original music. Support Radiolab by becoming a member today at     You can read The Transition Integrity Project's report here.