When visitors arrive at Edmonton International Airport in Alberta, Canada, they are greeted by a 1,440 square foot living wall; a “green wall” arranged like a modern art canvas with 8,000 plants encompassing 32 different species. “It is the largest living wall inside any building in the world,” says Patrick Poiraud, design consultant and principal with Green Over Grey, the designers behind the installation.

Green walls provide an injection of nature that promotes relaxation and (in the case of hospitals) healing. But green walls also serve a vital role in protecting and insulating buildings, provide a means for reducing runoff, help lower indoor air pollutants and increase biodiversity by creating mini-ecosystems on the outside of buildings.

As cities expand, they can’t always incorporate parkland into all the added concrete. Instead, says Poiraud, they can instead go vertical and incorporate green walls.

French botanist Patrick Blanc is credited with having created the first vertical garden at the Museum of Science and Industry in Paris in 1988. Blanc has gone on to design and install some of the world’s most famous green walls including one covering the office wing of Paris’ Quai Branly Museum that’s 8,600 square feet.

As the technique has gained popularity, others have refined methods for creating and installing the walls.

Green Over Grey constructs green walls that are lightweight, fully hydroponic, and make use of plants that are at home growing on cliffs or the sides of trees —plants, in other words, used to little or no soil. Poiraud and his partner traveled the world to assess the potential of vertical-growing plants, visiting tropical rainforests in Malaysia, Papua New Guinea and Brazil. What they found were lots of varieties of epiphytes or “air plants,” plants that grow non-parasitically on other plants and draw nutrients and water from the air and rain.

Without the need for soil, the designers have significantly more control over the way plants are arranged allowing the green walls to become living art. Poiraud says there is no limit to the dimensions they can plant, as even with mature plants their green walls weigh just four to five pounds per square foot.

Living Wall at Edmonton International Airport Courtesy Green Over Grey/Merle Prosofsky

The designers’ first step is to attach a frame fitted with waterproof panels to the building’s existing envelope. They leave a layer of air between the frame and the building and then install an automatic drip irrigation system. A porous material takes the place of soil and a huge number of plants can be used—including perennials, foliage plants, mosses, bushes and even small trees.

Meanwhile, Plant Connection, Inc., based in Long Island, New York, begin with their own GroWall panels that are planted (with soil) in a greenhouse until the plants mature—in this way the plants’ roots push against the panel and stay anchored in place. Each panel is hung on brackets that sit about half an inch off the wall, allowing for air flow. These installations, too, feature drip irrigation tubing and catch basins. The biggest maintenance issue is making sure the irrigation system is working properly.

Plant Connection has installed a three-story green wall in the stairway of a NYC office building, and their system was used to form the 30’ long living architectural centerpiece of Boston restaurant Sweet Caroline’s which has been dubbed “the Green Monster.

Adding Green to Green

Living walls automatically add points towards a building’s LEED (Leadership in Energy and Environmental Design) rating, but there are additional steps that can be taken to maximize their efficiency.

“You can make it more sustainable by collecting rainwater from the roof,” to use for irrigation, Poiraud notes. “Rainwater harvesting decreases the water going to the sewage treatment plant.”

Storms and heavy rains have little impact on the structures, which in fact function to protect and better insulate the building. “If you have a green wall on a large wall, especially a south-facing wall,” Poiraud says, “you’ll see an effect on the building that’s similar to a green roof, decreasing heating and cooling costs by 15 percent.”

Other benefits include acoustic dampening. Green walls help reduce noise pollution indoors and outdoors and act as a refuge for local pollinators and birds, particularly when native plants are used.

Green Over Grey is currently at work on a massive bridge installation in Western Canada that’s three times the size of the living wall at the Edmonton airport that Poiraud said will be unveiled in the spring of 2013.

Reprinted from Ecomagination.