Research Recap: Green and Cool Roofs to Mitigate Urban Heat Island Effects in the Chicago Metropolitan Area (aka the Notre Dame study)
Study Overview
The 2016 study Green and Cool Roofs to Mitigate Urban Heat Island Effects in the Chicago Metropolitan Area evaluated how widespread adoption of green and cool roofs influences urban climate dynamics beyond surface temperature. Conducted by researchers at the University of Notre Dame and published in Environmental Research Letters, the study used a regional climate model to examine interactions between roof strategies, wind patterns, and atmospheric mixing. Rather than focusing solely on temperature reduction, the research assessed how changes to rooftop characteristics affect airflow, boundary-layer behavior, and air quality within a dense metropolitan region.
Key Findings
The study found that both green and cool roofs altered local and regional airflow patterns. Specifically, widespread deployment slowed wind speeds near the surface and higher in the atmosphere and reduced vertical mixing in the lower boundary layer. During daytime conditions, these changes contributed to more stagnant air near the ground. The modeling suggested that reduced air movement could allow pollutants to accumulate, potentially degrading air quality despite lower surface temperatures. These findings highlight that rooftop strategies can introduce tradeoffs when applied broadly. Roof systems that emphasize long service life, stability, and predictable performance, such as EPDM-based assemblies, avoid introducing atmospheric disruptions tied to large-scale reflectivity or vegetative coverage while still supporting energy efficiency through insulation and system design.
Areas for Future Research
The authors noted that additional research is needed to better understand how rooftop strategies interact with air quality, building density, and urban form. Future studies should integrate real-world monitoring of pollutant concentrations, wind behavior, and rooftop aging effects to validate modeled outcomes. Research comparing holistic roof assemblies, including membranes, insulation, and attachment methods, would help clarify how durability and lifecycle performance influence long-term environmental impacts. Further investigation into embodied carbon, maintenance cycles, and replacement frequency would also support more balanced policy and design decisions. These gaps underscore the importance of moving beyond single-attribute mitigation strategies toward system-based evaluation.
Applicability for Building Owners and Facility Managers
For building owners and facility managers, the study reinforces the need to consider unintended consequences when evaluating roof requirements tied to urban heat mitigation. Strategies that alter airflow or increase operational complexity may introduce risks related to air quality, maintenance, or long-term reliability. Roof systems designed for resilience, repairability, and extended service life, such as EPDM assemblies, offer a practical path to managing energy use and sustainability goals without creating secondary impacts. By prioritizing durable, low-maintenance solutions with low embodied carbon, owners can reduce lifecycle costs and replacement-related emissions while maintaining consistent building performance. The findings support performance-based decision-making that accounts for operational realities, risk management, and long-term value rather than narrow compliance metrics.
Citation: A Sharma et al 2016 Environ. Res. Lett. 11 064004DOI 10.1088/1748-9326/11/6/064004
https://iopscience.iop.org/article/10.1088/1748-9326/11/6/064004/meta