Urban areas experience increased temperatures due to the urban heat island effect, caused by concrete sidewalks, black asphalt streets, and brick and steel buildings that retain heat. These rising temperatures are a concern for cities like Chicago, especially during the summer months. To combat this issue, researchers at the U.S. Department of Energy’s Argonne National Laboratory examined three roofing strategies and their impact on near-surface temperature and cooling energy demand in the Chicago metropolitan area.
The study focused on three types of roofs: cool roofs, green roofs, and solar panel roofs. Cool roofs are painted with a heat-reflecting white coating, green roofs have vegetation, and solar panel roofs generate electricity from the sun.
The results of the study showed that all three roofing strategies reduced the near-surface temperature and air conditioning (AC) consumption during the daytime hours when temperatures are highest. Cool roofs had the greatest impact, reducing the near-surface temperature by 1.5 degrees Celsius, followed by green roofs at 1.2 degrees and solar panel roofs at 0.6 degrees across the Chicago area. In terms of AC energy consumption, cool roofs had the most significant reduction at 16.6%, followed by green roofs at 14.0% and solar panel roofs at 7.6%.
The large-scale deployment of cool roofs demonstrated the most potential for cooling effects and energy savings. Cool roofs are also the most cost-effective option and do not require additional water. However, they do not assist in managing stormwater loads like green roofs do. Stakeholders can use these findings to inform sustainable development approaches and minimize greenhouse gas emissions in the long term.
The research was conducted as part of CROCUS (Community Research on Climate & Urban Science), a collaborative effort led by Argonne in partnership with academic and community organizations. CROCUS focuses on studying urban climate change and its implications for environmental justice in the Chicago region. The results of this study will help CROCUS communities plan and test mitigation options to combat the urban heat island effect.
The researchers aim to develop city-scale and global-scale models for each of the roofing options. To achieve this, they will work on gathering more measurements and data for green roofs, as there is currently limited information available. They will also measure the roofs of CROCUS partners throughout the city to improve the representation of green roofs in the models. Additionally, the researchers plan to improve the resolution of the model to better understand the impact of trees and other factors at the street level.
The research utilized supercomputing resources at the Argonne Leadership Computing Facility (ALCF) and the National Energy Research Scientific Computing Center (NERSC). These facilities, located at Argonne and Lawrence Berkeley National Laboratory, respectively, provided the computational power needed to run the regional climate model and analyze the data.
Roofing strategies play a crucial role in mitigating the urban heat island effect in cities like Chicago. The study highlighted the effectiveness of cool roofs in reducing temperatures and energy consumption, while also emphasizing the importance of incorporating green roofs and solar panel roofs for their additional benefits. The research conducted by Argonne’s CROCUS project provides valuable insights for decision-makers and communities looking to create sustainable and resilient urban environments. With further advancements in modeling and data collection, future studies will continue to refine the understanding of these roofing strategies and their impact on urban heat island effects.
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