Green roofs

April 17, 2011

Green Roofs Take Root
By Kristi Kates
Installed on top of homes, businesses, and factories, among other
buildings, green roofs - also called eco-roofs or living roofs - are
perhaps one of the more unusual ‘green’ movements going on today.
The benefits of green roofs are many. They include conserving energy,
lowering roof temperatures, cleaning the air, reducing noise inside the
building, creating mini-habitats for wildlife, and extending the life of
the roof itself.
But while a green roof is definitely worth the effort, it’s also not just
as simple as throwing some dirt and plants up on top of an existing roof.
It’s a far more complicated endeavor that involves quite a bit of
pre-planning - and that has been subject to more than a few
misunderstandings about its feasibility in northern climates like
Michigan.

MICHIGAN TO ALASKA
“Certainly the window of opportunity to plant a green roof is a more
narrow one in Michigan, than, say, in Georgia,” Steven Peck, President of
Toronto’s GRHC (Green Roofs for Healthy Cities) organization, points out.
“But in terms of the technical aspect, there’s a bit of a fallacy about
that. I don’t think that anything about Northern Michigan poses any
significant challenge to having a green roof. Yes, Northern Michigan is in
a northern climate - but Yukon, Alaska is much farther north, and there
are green roofs there. There are some great environment things happening
in Michigan already.”
Peck says that there’s vegetation growing everywhere in the world - “you
just have to choose plants that can survive frost/freeze cycles,” he says,
“we collect info on green roofs from Hawaii to Alaska.”
Sod or moss roofs are perhaps a couple of the simplest forms of green
roofs, while others are called “intensive” or “extensive,” depending on
the depth of soil needed, the complexity of the plants, and the amount of
maintenance required. “Intensive” green roofs often resemble parks, and
can include things as tiny as cooking herbs and as large as small trees;
“extensive” green roofs aren’t generally walked upon, and only require
minimal maintenance and fertilizing.

GETTING STARTED
So you like the idea, but aren’t sure where to start? Well, as mentioned
above, a green roof may appear to be merely a layer of soil with greenery
planted in it - simple on the surface. But an actual healthy, safe,
useable green roof takes specialized planning, structural considerations,
and of course careful plant selection, as well; there are a number of
resources online that offer kits, explanations, and how-tos, but Peck
suggests that, in the long run, it might be something best done with
professional help.
“Green roofs really aren’t a DIY technology,” Peck says, “you have to have
professionals working on green roof projects. There are a lot of
structural things that need to be taken care of, or you can cause serious
damage to your home or building.”
One of the largest green roofs in the country can actually be found in
Michigan - at the Ford Motor Company’s River Rouge plant, where 450,000
square feet (more than 10 acres) of assembly plants were covered with
foliage. Chicago’s Millennium Park - which is actually built over the
Millennium Park Garage and one of the commuter rail stations - is another
example of a Midwestern-based green roof that the public may not even be
aware of, even as they’re strolling its grounds.
The basics are - well, basic. You start with a waterproof membrane (most
green roofs’ failures are said to involve water damage) and add a root
barrier, such as concrete.
Next, you add a drainage layer like gravel to carry excess water to
gutters and off of your roof. A filter fabric will help to hold your next
step - your growing medium (soil mixtures) - in place. And an irrigation
system will keep your plants healthy without wasting water.
And finally, it’s all about the plants.

CHOOSING THE GREENERY
  The possibilities are many when deciding what plants to include on your
green roof. Depending on the size of the roof and, again, that structural
foundation (properly done, of course), you may even be able to include
small trees, a light gazebo, or benches as part of your venture.
Common plants included in green roofs, in addition to mosses and grasses,
can be herbs such as chives, oregano, or thyme; flowers such as black-eyed
Susans, phlox, dwarf balloon flowers, bellflowers, or asters; and other
plants such as sedge, oatgrass, or the many varieties of stonecrop.
Your green roof might even be able to be more multi-colored via flowers
than you’d expect, making it a real standout in Northern Michigan, where
interest in green roofs is finally beginning to really catch on.

POPULAR ROOFS
But what about the heavy snows in this region, you might ask? That might
seem like a deal-breaker for a project that focuses on the growing season.
“Snow is not an issue for green roofs at all,” Peck reassures, “that’s
just something you take into consideration when you’re calculating the
roof’s structural loading capacity - snow is already part of that
consideration.”
Peck says that in 2010, the green roof industry grew by 28.5%, a great
indication that people are becoming more and more interested in
integrating green roofs into their homes and businesses.
“One of the reasons green roofs are growing so rapidly is that there are a
number of public and private benefits available for green roofs,” he
explains, “there are incentives and regulations to support the building of
them, which is helping the whole green roof industry.”

Get more info on green roofs via Peck’s company’s website,
www.greenroofs.org.