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Posted on: February 26, 2009

Oh, Grow Up!

They've sprouted in high-profile projects in cities here and abroad. Now, green roofs and walls are the next frontier - for home gardeners.

By Jennifer Parrish
CTW Features

Reinventing outdoor space: green rooftop on Chicago's city hall Image courtesy Mingo Design, Kari Elwell Katzander

Yearning for more garden space? Take heart. Gardens are sprouting up in some of the most unusual places. From the top of Chicago's City Hall, to the overhang on a San Francisco bus shelter, to a tree-topped roof of a Manhattan apartment complex, gardeners are discovering innovative ways to expand their garden space by installing "green" or "living" roofs and walls.

Long popular across the Atlantic, where Europeans have been known to graze their goats on their roof tops, living roofs and walls are part of a growing world-wide trend that has recently caught fire in the U.S. and Canada

A garden above your head

"Most of my customers are looking for a way to green their lives," explains Kelly Luckett of Green Roof Blocks, Florissant, Mo. Since 2004, his company has installed more than 50 green roofs, mostly on commercial buildings. Starting in 2007 his customer base has become increasingly residential, with clients looking to install green roofs over garages and single-family homes. What attracts these customers is not just a desire to have more garden space, but also to help the environment.

Living roofs provide a wide-range of advantages for nature and homeowners alike. These include increased longevity of the roofing structure, improved insulation and noise mitigation, absorption of air pollution and sequestration of greenhouse gases and a space for migrating birds and other wildlife to thrive.

Perhaps of greatest interest to environmentalists and municipalities is the capacity of living roofs to reduce sewer system loads and improve storm water management. Green roofs that have a depth of three inches of soil can absorb 75 percent of the water produced by a rainfall of a half-inch. And, because the rooftop vegetation acts as a filtration system, what water does escape is free from contamination by tar and other environmentally destructive substances, which can be found in the rainwater runoff of traditional roofs.

One person convinced was Chicago Mayor Richard Daley, who, since 2001, has been the champion of Chicago's aggressive movement to green roofs throughout the city. In 2007 alone, Chicago installed more than 500,000 square feet of green roof space and now has more living roofs than any city in the nation. Other cities have followed suit.

Living roofs vary in their design and structure - as well as their cost. The price for the installation of a typical green roof runs between twice and five or more times that of a traditional roof. Over a green roof's lifetime, however, the costs may even out, experts say. In fact, because the vegetation protects the underlying roofing materials from weatherization and ultraviolet radiation, a properly installed green roof typically lasts a minimum of 40 years.

Gardens go vertical

Take green roofs and flip them 90˚ and you have green walls. The brainchild of French botanist Patrick Blanc, living walls are currently the height of fashion in Paris - and growing in popularity here in the U.S. It all began one day when Blanc had an epiphany whilst observing that many plants grow vertically in nature, even on sheer rock face. In 2006 he created the now world-famous living wall for the Quai Branley Museum near the Eiffel Tower in Paris. Since then, Blanc has gone on to install green walls throughout the world. Designed for beauty, to serve as art and even to provide a readily accessible source of produce, green walls are suitable for both indoor and outdoor applications. Depending on their function, they can be created in one of two ways. Like Blanc's designs, some living walls rely entirely on climbing plant species to cover surface areas that can range from one to several stories high. Others are constructed by installing plants in niches cut out of the face of the wall at regular intervals. These walls can be designed with a built-in irrigation system to trickle water down the surface until all the plants have been properly hydrated.

Indoors, living walls purify air, but may require artificial lighting where sunlight is lacking. To help customers add a touch of nature to their interior décor, many companies now sell prefabricated living wall panels, with prices ranging from approximately $150 to $200 per panel.

Green walls are not solely decorative. Many are used as gardens, a source of produce and herbs within the easy reach of chefs in homes and restaurants. Moreover, the living wall of the future can be found in a new form of urban agriculture called sky farms. In Las Vegas, plans are in the works for a 30-story-high sky farm, whose living walls would grow more than 100 different crops and feed an estimated 72,000 people.