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Researchers study green roof effectiveness

People want to know if the benefit of a green roof is going to justify the cost.


Researchers from the University of Illinois have developed a reliability analysis–based methodology that can be used to evaluate green infrastructure performance, specifically demonstrated for evaluating green roof peak runoff reduction.

Published in the American Society of Civil Engineers’ Journal of Sustainable Water in the Built Environment, the authors of the paper, Reshmina William a graduate student and Ashlyn Stillwell a professor in civil and environmental engineering, characterize green roof failure graphically with a visual aid typically used in earthquake engineering: fragility curves.

The fragility curves plot the probability of failure with changing storm intensity to show the runoff reduction provided by a green roof compared with a conventional roof under different storm scenarios.

In an article published by the University of Illinois, William notes that the primary goal of the research is to facilitate communication between scientists, policymakers, developers and the general public about the financial risk and environmental benefit of installing green roofs.

“One of the biggest barriers to the acceptance of green infrastructures is the perception of financial risk,” William said. “People want to know if the benefit of a green roof is going to justify the cost, but that risk is mitigated by knowing when an installation will be most effective, and that is where our model comes in.”

The results of their model and risk analysis provide a snapshot of green infrastructure performance for a particular green roof on their campus. And while the results from a single model do not provide a thorough green infrastructure evaluation, William and Stillwell said that is one of the strengths of their technique. Its adaptability across different technologies and environments will make it essential to any green infrastructure analysis.