From the Hanging Gardens of Babylon to City Hall in Chicago
Photo: Edmund C. Snodgrass
Green roofs go a long way toward helping to create
a more sustainable world. While it may seem an unusual building
technique, green roofs go back as far as 600 B.C. to the hanging gardens
of Babylon in Iraq, built by King Nebuchadnezzar for his wife, Queen
Amyitis, who longed for the tropical gardens of her Persian homeland.
The gardens were terraced from the top of their palace to the ground,
providing all the fruits and flora she missed. According to legend, the
palace and their gardens were destroyed by earthquakes.
In past decades, green roofs have become popular
in Europe. Today, building regulations in Germany and Canada support
green roof development because of its improved sustainability,
longevity, and thermal and water-filtering qualities.
Now green roofs are gaining ground in the United States, too. Chicago
Mayor Richard Daley vowed that Chicago would be the city with the most
turf on its concrete skyline, greening City Hall in 2001. Currently, the
city has achieved his goal of more than 300 buildings - 7,000,000
square feet - of green roofs completed or under way. Washington, D.C.;
Minneapolis; and Baltimore also stand out as leaders in the green roof
revolution, according to www.greenroofs.org,
the website of Green Roofs for Healthy Cities. This organization
provides resources and education to help guide the way to rooftop
sustainability.
The U.S. Green Building Council® (USGBC®) announced a new award in September 2010, titled the "Mayor Richard M. Daley Legacy Award for Global Leadership in Creating Sustainable Cities." Mayor Daley was its first recipient, at the USGBC Greenbuild conference (November 17-19, 2010) in Chicago. USGBC said Chicago's Sustainable Development Policy mandates that projects receiving financial or zoning assistance from the city include sustainable elements such as green roofs, LEED® certification, or designs that allow structures to absorb large amounts of stormwater.
Chicago's Green Permit Program allows contractors to shave off as much as $25,000 from the building permit process by choosing to incorporate some of 12 sustainable design elements.
At What Cost?
Despite the up-front cost - from $5 to $35 per
square foot - green roofs provide multiple benefits that offset their
expense within a few years. The U.S. Environmental Protection Agency
estimates a five-year average to recoup costs.
Covering building tops with soil, sod, and gardens
provides a pleasant place to spend time, particularly in urban
environments; processes CO2 in the atmosphere; and produces
oxygen, provides food, and helps insulate buildings so they don't use as
much energy to heat or cool. The plants also help filter the air as the
breeze moves through them, pulling out particulates that can cause
respiratory illness.
"Green roofs intercept the solar radiation that
would strike dark roof surfaces and be converted into heat, thereby
improving energy conservation," said Hitesh Mehta, a landscape architect
who has designed many sustainable resorts around the world. He recently
released a guide to the world's most eco-friendly lodges, Authentic
Ecolodges (Collins Design, 2010). "Because green roofs reduce the
surface temperature of a roof by minimizing heat-absorbing surfaces, a
green roof helps to reduce energy costs inside the building as well.
Like urban forests and reflective roofing surfaces, they absorb and/or
deflect solar radiation so that it does not produce heat. The urban heat
island effect increases the use of more electricity for air
conditioners, and it increases the rate at which chemical processes
generate pollutants such as ground-level ozone. It also exacerbates
heat-related illnesses."
Intensive green roofs have deep soil that can support trees, shrubs, and lots of visitors.
Intensive green roofs have deep soil that can support trees, shrubs, and lots of visitors
Extensive or Intensive
Building a green rooftop involves installing a
waterproof barrier over the roof, then overlaying one to six inches of
soil. There are two systems of green roof design: extensive and
intensive. Both systems include rainwater catchments that send the
filtered runoff into barrels for landscape irrigation, either feeding
back to the roof garden during droughts or to surrounding yards and
preventing runoff that typically pollutes waterways and groundwater.
Extensive roof design is the most
lightweight with the least amount of soil. It supports water-retentive
plants such as succulents, which need little maintenance once
established.
Intensive design uses a deeper soil level to support vegetables and even trees for a productive garden.
"An intensive green roof is usually specified when
the green roof goals are aesthetic, versus simply economic, in nature
whilst an extensive green roof is primarily implemented for
environmental and economic purposes," said Mehta.
The layer of soil helps moderate the temperature within the buildings underneath the rooftop garden, and the landscape maintains a lower temperature than a typical roof - as much as 25 to 80 degrees lower. A study conducted by Environment Canada found that a typical one-story building with a grass roof and 3.9 inches of growing medium reduces summer cooling needs by 25 percent. A six-inch extensive green roof can reduce heat gains by 95 percent and heat losses by 26 percent. Chicago City Hall has recorded roof temperatures 100 degrees cooler than a neighboring building with traditional roofing.
The steep slopes of the roof at the California Academy of Sciences act as a natural ventilation and cooling system.
Photo: Courtesy of Green Roofs for Healthy Cities (www.greenroofs.org) and Rana Creek Living Architecture.
A Healthier Planet
Intensive roof gardens can add to the local
economy by producing food that provides greater nutritional value to the
community because it's accessible immediately from the garden, without
travel time. In addition, the visual benefit of adding greenery,
particularly to the urban landscape, has been shown to reduce stress and
to have therapeutic health benefits, which accelerates recovery from
illness. Rooftop gardens also increase habitat opportunities for birds,
bees, and other insects.
Green roofs are a great example of how creating more sustainable ways of doing things can benefit the planet, its people, and even their pocketbooks.
Rancho Margot
Rancho Margot boasts nearly 200 hectares of
rolling hills nestled against one of Costa Rica's marvels, the Arenal
Volcano, which constantly rumbles, smokes, and, occasionally, tosses
fire. Juan Sostheim and his family have created a fully sustainable
ranch here. The staff of 43 and about 15 volunteers welcomes up to 100
guests at a time.
The ranch is powered by hydropower from streams
running across the property as well as waste from the chickens, pigs,
and cattle raised on the organic produce grown from the farm. "We throw
away about what a family of four discards in the U.S. Every bit of the
trash we produce is sorted through twice. We recycle everything we can
here," said Sostheim. "One ton of compost produces 23 million BTUs, and
that equals 5,000 kilowatts of power for us."
Sostheim uses excess power to heat the hot pool, a
cave-like, stone-lined pool where guests can relax in the evenings. An
open-air massage bungalow and morning yoga add to the ambience.
The ranch farm provides organic food for the hotel
and produces its own soaps for guests. Horses are available for rides
to mountainside waterfalls or the nearby volcano. Sostheim even has
established a wildlife sanctuary to care for local squirrel and howler
monkeys that have been rescued from civilian life and are released back
to the wild when they're ready.
For information on visiting or volunteering at the ranch, go to: www.ranchomargot.org.
Bell Book & Candle
A new restaurant in Greenwich Village, Manhattan,
Bell Book & Candle takes a different twist on the green roof idea.
The restaurant is supported by a rooftop of state-of-the-art
hydroponics. Chef John Mooney grows a substantial amount of the herbs,
greens, and vegetables served to his patrons in self-supported towers of
greenery atop the restaurant. It's one of the first restaurant in the
United States that grows its own food on its roof.
Space-saving vertical towers flood plants with
nutrients, water, and sun. "The towers provide a nutrient-rich solution,
using no soil," Mooney told CNN audiences. "They'll never see a
refrigerator. They're not going to be gassed, and they're not going to
be treated in any way for transport. I just pluck them straight from the
vine. It makes a difference. This is the wave of the future for home
and commercial use. Roots are attached, so they stay with the plant
until it's prepared in the kitchen. I call it living lettuce."
Check it out at:
141 West 10th Street
New York, NY
(212) 414-2355
Trish Riley is the author of The Complete Idiot's Guide to Greening Your Business and The Complete Idiot's Guide to Green Living, publisher of www.gogreennation.org, and director of Cinema Verde (www.verdefest.org), an environmental film festival. Originally published in Drive magazine. Shown here with exclusive web content.
