Green walls are becoming more and more common place in cities across the world. However, they are usually implemented as apart of a new architectural design rather than an existing building. Until recently when a 2,380 square-foot, six storey high green wall was installed by PNC on their existing corporate headquarters in Pittsburgh. The wall is a modular design and is two foot by two foot panels(approx. 600 x 600mm). The wall was installed by Green Living Technologies and according to the video below is the largest green wall in North America and is planted with different plant species that will create an evergreen wall all year around.
According to the report by Sarah Amandolare at Finding Dulcinea
The average cost per square foot of green wall is between $100 and $125, according to George Irwin of Green Living Technologies LLC
another technique open to those interested in green walls are using soil pockets – they give the plants more growing room creating a more 3 dimensional effect http://www.gardenbeet.com