Green Roofs - Living Architecture Monitor Fall 2020 - 36

ON SPEC

WIND UPLIFT ON GREEN
ROOFING - IS IT OVERBLOWN?
BY LIZ MORRIS, GRP

A

fter several decades of experience in North America,
green roof designers, suppliers and installers have spent
a lot of time perfecting their trade. The industry has
learned a great deal about how to install vegetated roofing that is thriving, leak-free, and long-term (as in, lasting for
many decades).
As the world of living architecture continues to mature, we are
now we are expanding into new realms never thought possible.
For example, the University of Miami is in the middle of a hurricane super-highway. Until recently, not much green roofing happened in hurricane zones, due to concerns about keeping green
roofs on buildings during very high winds. But this campus's 25
new green roofs were accepted by Miami-Dade for high velocity
hurricane zone wind resistance, and are the new standard for
protection against wind uplift.
Considering that hurricane zones are generally located in
highly sensitive coastal environments, it is especially important
that we are able to utilize the most impactful aspect of sustainable
urban development in these areas - which is the reintroduction
of vegetation through living architecture. These fragile watershed
ecosystems can benefit significantly from on-structure vegetation,
especially due to improved stormwater management, reduced
urban heat island effect, and enhanced air quality.
It's not just hurricane zones that call for withstanding strong
winds. Non-coastal cities located on fresh waters also can experience
damaging gusts through lake- and canyon-effects. High-rise green
roofing on skyscrapers in any wind zone must consider the potential
for displacement of the green roof components in strong winds.
So how to design in hurricane zones? It is important (even
without on-structure vegetation) to get a comprehensive underLIVING ARCHITECTURE MONITOR / FALL 2020 / 34

standing of the wind conditions on site. Whether caused by other
buildings, high-rise conditions, or location in a hurricane zone,
the first step is knowing the various wind-uplift scenarios each
roof area will experience.
The next step is ensuring the system configuration can
withstand the rooftop conditions without displacement of any
components. Generally, the edges of the roof are most sensitive
to wind uplift, but can be secured with the use of vegetated free
zones of strapped or otherwise secured pavers. Or, in the case of
the University of Miami Lakeside Village housing, their green
roofs have a double parapet wall, which left a non-vegetated wind
tunnel around the perimeter of each roof, to channel the wind
away from the greenery.
Another consideration is the use of insulation and drainboards,
both of which could introduce the potential for uplift if not sufficiently ballasted and secured. The use of soil stabilizers, such as
several layers of mesh within and on top of the growing media,
can help keep it in place during high winds. But planting is also
key to protection against wind scour - thriving roofs with full
coverage of vegetation will hold their growth media in place more
effectively than sparse, unhealthy plantings.
As green roofs and living walls become increasingly commonplace, and the benefits clearer and increasingly measurable,
we can now begin to expand into hurricane zones, urban high-rise
conditions, and cities with strong lake effects - which happen to
be areas that can most benefit from living architecture.
Liz Hart Morris, CDT, GRP, Director of Green Roofing, Henry serves
on the board of GRHC and has recently published a course on Why Green
Roofs Fail and What to Do About it on the Living Architecture Academy.
LIVINGARCHITECTUREMONITOR.COM


http://www.LIVINGARCHITECTUREMONITOR.COM

Green Roofs - Living Architecture Monitor Fall 2020

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Green Roofs - Living Architecture Monitor Fall 2020 - IP
Green Roofs - Living Architecture Monitor Fall 2020 - Cover1
Green Roofs - Living Architecture Monitor Fall 2020 - Cover2
Green Roofs - Living Architecture Monitor Fall 2020 - Table of Contents
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