Concrete sidewalks, black asphalt streets, and brick and steel buildings are all common elements of urban cities that contribute to and exacerbate the urban heat island effect. As temperatures continue to rise, it is crucial for decision-makers and communities to have access to information about strategies that can help keep residents cool. One such strategy involves utilizing roofs of buildings to help cool the surrounding outside air and reduce the need for air conditioning. Researchers at the U.S. Department of Energy’s Argonne National Laboratory conducted a study to understand the impact of different roofing strategies on near-surface temperature and cooling energy demand in the Chicago metropolitan area.
The Study
The researchers at Argonne National Laboratory conducted regional modeling in the Chicago metro area to simulate the effects of three different types of roofs: cool roofs (painted white to reflect heat), green roofs (covered in vegetation), and roofs with solar panels. The study focused on a heat wave event, where temperatures reached the 95th percentile observed in the city for three consecutive days.
The study found that all three types of roofs were effective in reducing near-surface temperatures and decreasing AC consumption during the hottest hours of the day. Cool roofs had the most significant cooling effect, reducing the near-surface temperature by 1.5 degrees Celsius, followed by green roofs (1.2 degrees) and solar panel roofs (0.6 degrees) across the Chicago area. The cooling effects of these roofs also led to a reduction in AC energy consumption, with cool roofs reducing energy demand by 16.6%, followed by green roofs (14.0%) and solar panel roofs (7.6%).
Cool roofs were identified as the most cost-effective option due to their lower cost compared to green roofs and solar panel roofs. Additionally, cool roofs do not require additional water, unlike green roofs. However, it is important to note that green roofs have the potential to manage stormwater loads, which cool roofs do not offer. The study’s results can be used by stakeholders to inform sustainable development approaches and minimize greenhouse gas emissions in the long term.
The study conducted by Argonne National Laboratory is part of the Community Research on Climate & Urban Science (CROCUS) Urban Integrated Field Laboratory, which focuses on studying urban climate change and its implications for environmental justice. The researchers plan to expand their study by developing city-scale and global-scale models for each of the roofing options. To achieve this, they will work on improving measurements and understanding of green roofs by taking surface and building-level measurements. The researchers also aim to improve the resolution of their models to the street scale to assess the cooling effects of elements such as trees on nearby buildings and pavements.
The study conducted by researchers at Argonne National Laboratory demonstrates the potential of different roofing strategies in mitigating urban heat. Cool roofs, green roofs, and solar panel roofs all show promise in reducing near-surface temperatures and cooling energy demand. The study’s findings provide valuable information for stakeholders and communities in making informed decisions about sustainable and energy-efficient development approaches. With further research and improvements in modeling, these roofing strategies can play a vital role in combating urban heat and reducing the carbon footprint of cities.
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