Cities are often plagued by the urban heat island effect, where common elements like concrete sidewalks and brick buildings retain heat and cause temperatures to rise. This phenomenon poses a significant challenge, especially during the summer months, and it is crucial for decision makers and communities to have access to strategies that can help keep urban residents cool. One such strategy involves utilizing rooftops to mitigate the effects of urban heat islands. In a study conducted by researchers at the U.S. Department of Energy’s Argonne National Laboratory, three different types of roofing strategies were examined to understand 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, which are painted a heat-reflecting white, have the ability to reduce near-surface temperatures by 1.5 degrees Celsius. Green roofs, which are covered in vegetation, can reduce temperatures by 1.2 degrees Celsius. Solar panel roofs, on the other hand, reduce temperatures by 0.6 degrees Celsius while also generating renewable energy.
The research findings indicate that all three roofing strategies contribute to a reduction in near-surface temperature and a decrease in air conditioning (AC) consumption. Cool roofs had the most significant cooling effect, reducing AC energy consumption by 16.6%. Green roofs followed closely behind, with a reduction of 14.0% in AC energy demand. Solar panel roofs showed a more moderate reduction of 7.6% in energy consumption.
Among the three strategies, cool roofs showed the greatest potential for cooling effects and energy savings. These roofs are not only cost-effective but also require no additional water. However, it is essential to note that cool roofs do not contribute to stormwater management, which is a benefit provided by green roofs.
The results of this study can be instrumental in informing sustainable development approaches in urban areas. By implementing these roofing strategies, stakeholders can lower summertime cooling energy demand, reduce greenhouse gas emissions, and take steps towards environmental justice. The study serves as a valuable tool for communities in the Chicago region as they plan and test mitigation options to combat urban climate change.
While the current study provides a solid foundation, there is still room for improvement and expansion. The researchers at Argonne National Laboratory aim to develop city-scale and global-scale models for each of the roofing options. To achieve this, they plan to collect more data on green roofs by measuring energy input and output, water requirements, and retention rates. These measurements will enable them to refine calculations and models.
Additionally, the researchers will collaborate with CROCUS community organizations and members to measure the roofs of partner buildings throughout the city. This data collection process will provide a more comprehensive understanding of the impact of different roofing strategies on urban heat islands.
Furthermore, the researchers seek to improve the resolution of their model by incorporating street-scale data. This level of detail will enable them to discern the varying effects of trees and buildings on temperatures. Questions such as the cooling impact of a tree on nearby buildings and pavements can be answered with increased model resolution.
The team behind this research utilized supercomputing resources at the Argonne Leadership Computing Facility (ALCF) and the National Energy Research Scientific Computing Center (NERSC). These facilities, which are user facilities of the Department of Energy’s Office of Science, provided the computational power necessary for running the regional climate model simulations.
As cities grapple with the challenges posed by urban heat islands, innovative solutions are necessary to combat rising temperatures. The utilization of different roofing strategies, such as cool roofs, green roofs, and solar panel roofs, can significantly contribute to temperature reduction and savings in energy consumption. The research conducted at Argonne National Laboratory highlights the importance of these strategies in mitigating the impact of urban heat islands and provides valuable insights for communities and decision makers in their pursuit of sustainability and climate resilience.