www.landscapeirrigation.com Landscape and Irrigation October 2016 31
Conservation Land Stewardship (CLS), housed within the
same building.
The results were very enlightening for us, confi rming some
assumptions and dispelling others:
■ Smaller rainfall events (typically less than 0.25 inches
of rainfall in an 8-hour period) resulted in zero runoff;
■ Larger events, and/or events immediately following
another rain event, produced runoff, but at a reduced volume
and peak discharge time;
■ Generally, the systems with deeper growing media
retained more water than the thinner systems;
■ Approximately 75 percent of the total annual runoff
volume was attenuated entirely on the green roof.
We also observed anecdotally that the building's upper fl oor
was noticeably quieter (it is situated across the street from a busy
rail line). Annual energy use fell by approximately $1,400, or
about 15 percent, with the addition of the green roof. Our staff
loved having a small "community" garden space to grow fl owers
and vegetables, and go out onto for breaks and lunches.
We have since designed a number of green roofs as part
of an overall approach to balancing rainwater on-site to the
degree possible, and continue to explore the potential to benefi t
PHOTOS COURTESY OF CONSERVATION DESIGN FORUM
from green roof performance at the site, neighborhood, and
community scale. Green roofs clearly play a critical role in urban
stormwater mitigation, and equally clear is the need for further
research and ongoing monitoring of stormwater performance on
green roofs in different climactic regions.
David Yocca, FASLA, is a senior partner and principal landscape
architect at Conservation Design Forum (CDF), and a member of
the Board of Directors for Green Roofs for Healthy Cities. CDF is a
restorative planning, design, and engineering fi rm.
This article originally appeared in Living Architecture Monitor,
the offi cial publication of Green Roofs for Health Cities, and
is reprinted here by permission. For more information, visit
www.livingarchitecturemonitor.com.
FIND OUT MORE
■ Final Report on the EPA 319 Grant and Project: http://www.cdfinc.com/
■ Article on CDF Green Roof Study by Bruce Dvorak: https://www.researchgate.
net/profile/Bruce_Dvorak2/publication/258310905_Green_Roof_Test_
Plots_A_Green_Roof_Comparison_Project_The_Illinois_EPA-CDF_Green_
Roof/links/546a51f40cf2397f783016b5.pdf
