Imagine a 2,300-square-foot garden, then imagine it hanging from a Downtown building. Smaller versions exist in cities worldwide, but Pittsburgh's first will be North America's largest.
Called a "living wall" or a "sky farm," this engineering and design feat brings together compatible plants in 602 panels of contained soil. Stainless-steel brackets and panels will anchor it to the southeast-facing wall at One PNC Plaza, Fifth Avenue and Wood Street. The goal is to have it in place by Sept. 14, said Susan Golomb, vice president of realty services for PNC Financial Services Group.
PNC asked BD&E, a Downtown branding and marketing firm, to produce "a concept that would make it clear this was our headquarters and part of a larger campus," said Ms. Golomb.
Principals at BD&E proposed incorporating the sign within a living wall, she said.
"PNC, being committed to sustainability, really embraced the idea." (PNC claims to have more green buildings than any company in the world.)
Besides the visual wow of it, the living wall will save on costs, insulating the building in summer, because plants reflect about one-fifth of the sun's heat, and insulating it from heat loss in winter. Like all gardens, it will absorb CO2 and provide oxygen.
"We thought it would also become a destination, almost an art exhibit for PNC," said Kristina Martinez, a principal at BD&E.
When fully watered by drip irrigation, the garden will weigh about 24 tons. PNC asked for and got planning commission approval on July 21, a hastening of the normal process, in order to install the garden in time for the G-20 summit, Sept. 24-25.
As for the cost, Fred Solomon, a spokesman for PNC, said, "We don't disclose these kinds of expenses."
Construction began this week. A scaffold will remain during removal of granite panels on the side of the building, prepping of the wall, installation of a base -- wood from sustainable forests, waterproofed -- and installation of the panels.
The plants were chosen for climate tolerance, sunlight cycles and changing color patterns and texture, said Ms. Golomb. "We wanted it to be like tapestry."
Root systems intertwine with the plants' housing. Water will drip through the panels, draining minimally into a catch basin at the bottom.
Mike Cenkner, owner of Coraopolis-based Cenkner Engineering Associates Inc., said this living wall is his firm's first.
"It's been a lot of fun, very exciting. All of our staff here really thrives on challenges," he said.
Mr. Cenkner, which has worked with PNC on other projects, is preparing the site ahead of installation and working with Green Living Technology, a Rochester, N.Y., firm that designed the structure and irrigation system.
The plants include variegated carex, heuchera, a variety of evergreen ferns, Euonymus 'Kewensis,' Lysimachia 'Aurea,' and varieties of sedum and ajuga.
Kari Elwell Katzander, owner and founder of Mingo Design in New York City, designed PNC's living wall and has designed seven others in and around New York City.
"The design challenges when you go vertical are dealing with how sunlight is going to pull the plant in different directions and making sure the plants are grouped" for opportune water distribution, she said.
"As a designer for about 24 years, I am thrilled to have such a large canvas to work on. [PNC] allowed me creative freedom."
The colors will stay true to the design, with some blurring of lines when plants flower.
"Imagine standing in one place looking at a group of plants as if you could see it through time-lapse photography," she said. "The lime green foliage in the spring turns darker green in the summer, then it flowers and the flowers get bigger and bigger and then they yellow in the fall. That's just one plant. There are evergreens that turn burgundy."
The world is dotted with living walls. The Whole Foods Market in Vancouver has one. Queens College in Ontario has one. They exist in Paris, Tokyo, Brussels, London and Gdansk, Poland. In some countries, such as the Philippines and Costa Rica, people farm them.
"Imagine how much vertical space there is in cities," said Ms. Elwell Katzander, noting the need for smog mitigation.
"The door is wide open for more of these. Space is valuable. If you want to green it, green it up."