Green Roofs
By Katie Navarra
Getting Started with Green Roofs
Your primer to green roof benefits, trends and getting involved
ooftops in the United States were
traditionally only thought of in
terms of their structural value. But
with a growing interest in sustainability, building owners, architects,
engineers and landscape companies recognize rooftops as an opportunity to manage
stormwater, reduce the effects of the heat
island, improve a building's insulation value
and provide a natural habitat in cities that
have become concrete jungles.
R
Photos by John Magill
10 Landscape and Irrigation September 2013
A new revenue source and/or tax credits can be added benefits of green roofs depending on the geographic location and
local laws.
A green roof, also called a living roof, is
a rooftop that incorporates partial or full
vegetation. A growing medium is spread
over a waterproof membrane and plants
are added. Depending on the site, root barriers, drainage and/or an irrigation system
may also be a part of the green roof.
Green roofs have been around for centuries, with roots in Northern Scandinavia.
The green roof concepts used today were
first used in Germany more than 30 years
ago. In recent years, green roofs have become increasingly popular in the United
States.
"A green roof retains storm water, insulates the building thermally and acoustically, prevents the Urban Heat Island
effect, and provides habitat for people and
wildlife," said John Magill, M.S. Horticulture, Green Roof Professional in Illinois.
He added that green roofs are also creating
a habitat for unusual, rare, ground nesting
species that have been virtually been
wiped out by cats at grade level.
"Based on the level of maintenance,
depth of the planting media, and types of
plants, there are two or three types of
green roofs: extensive, intensive, and a
combination of both," said José Magan,
owner of Accent Urban Design, a landscape and urban design and land planning
firm in Homewood, Ill.
An extensive green roof can support 10
to 25 pounds of plant life per square foot,
whereas an intensive green roof can support 80 to 150 pounds of vegetation per
square foot.
Intensive green roofs typically include
grass, shrubs and other plants that require
regular maintenance compared to extensive green roofs that are designed to be
self-sustaining.
"Even though all new plantings need
water until they are established, the use of
irrigation is optional and it depends on the
climate and particular needs of each green
roof," said Magan.
As with traditional landscape designs,
the project owner and designer can take
liberty in selecting the look and plant material included; however, "there are two
main goals in the design of every green
roof," said Magan. "Protect the integrity of
the waterproof assembly, and guarantee
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