A request to build the greenest high-rise in the world is a tall order. But that’s precisely what Gary Saulson, executive vice president and director of corporate real estate for PNC Financial Services Group, asked of the design team behind the company’s new headquarters, the 33-story Tower at PNC Plaza in Pittsburgh, which will exceed LEED Platinum standards when it opens in 2015.
The design team, including Gensler and sustainability consultants Paladino & Co., established three pillars that guided each design decision: community building, workplace innovator, and climate responder. The tower’s passive and active features encourage employees to take ownership of their workspaces. The breathing building is wrapped by a double-skin façade with a motorized outer layer and manually operable inner layer. Outdoor spaces interspersed throughout the building include a semi-conditioned atrium, dubbed the “community porch,” as well as green terraces at setbacks, providing a diverse array of collaborative workspaces.
In designing the base of the tower, the architects focused on activating the street-front with retail spaces. The lobby, nicknamed the “urban room,” is transparent and inviting, unlike the typical fortresslike entries to headquarters’ buildings. PNC’s roots are in Pittsburgh, and it is committed to investing in the city. The plans for its headquarters have already proven a catalyst for redevelopment in downtown’s Market Square area, where the completion of Three PNC Plaza three years ago spurred the opening of many new businesses. To that end, the tower’s program does not provide a full-service cafeteria, and instead encourages employees to venture out at lunchtime and support local restaurants.
For over 40 percent of the year, the Tower at PNC Plaza will achieve net-zero-energy status through daylighting—narrow floorplates allow light to penetrate all workspaces—and an innovative passive cooling system that operates via a chimney effect to naturally ventilate the building without using fan power. The sloped cap of the tower, the building’s “fifth façade,” is outfitted with solar collectors that heat air within a large glass box connected to a shaft that runs through the mechanical core. A series of motorized louvers and actuators in the double-skin façade draws fresh air across the floors, where it is heated and then drawn through the shaft to be exhausted out the top of the roof.
Three rivers define the landscape of Pittsburgh, but they are endangered by wastewater and stormwater runoff from the city’s frequently overburdened systems. In order to preserve occupants’ views of the rivers, as well as provide a responsible model for downtown developments, the Tower at PNC Plaza will use little potable water thanks to low-flow fixtures and a rainwater harvesting system to irrigate the green roofs. Systems will fully treat gray- and blackwater.
Materials and IAQ
The team behind the Tower at PNC Plaza took advantage of Pittsburgh’s legacy as “the Steel City” for the building’s structural system. For the inner layer of the double-skin façade assembly, the designers debated using standard aluminum over an outside-the-box option—wood. Aluminum contains a lot of embodied energy, and it requires extensive thermal breaking as part of an enclosure system. Wood proves a better insulator and also lends a warmer look to the interior spaces. Ultimately, the team selected FSC-certified red maple grown in western Pennsylvania for the interior curtainwall.
“People have become very passive in how they occupy the buildings in which they work, which are often sealed and air-conditioned boxes. There’s an expectation that the interior is a constant 68 degrees, and otherwise, we’re uncomfortable. We’re giving people the opportunity to control their environment. They must take responsibility for their own comfort and, in turn, they will become very much a part of the performance of the building.” —Hao Ko, senior associate and design director at Gensler
“As occupants learn how to use the spaces, and as building operators gain more confidence in the users, the performance of the building will get better over time, whereas performance typically decreases in the traditional model.” —Brad Pease, building science practice area director and project manager, Paladino & Co.
“It’s hard to do a double-skin project in the United States. Is this too much fantasy? … I admire the level of thinking that went into some of the passive strategies, but one of my questions is if this project will really work. I think they put good thought into it, but I want them to prove it. … If they build it, I will love it. … There’s something to be said for promoting large commercial projects for their environmental performance. Talk about having an impact: If they can do all of these fabulous things that we question whether they will get executed, it could have significant impact.”
Architect, interior designer: Gensler, gensler.com
Client, owner: PNC Financial Services Group, pnc.com
Mechanical engineer, structural engineer, electrical engineer: Buro Happold Consulting Engineers, burohappold.com
Civil engineer: Civil and Environmental Consultants, cecinc.com
Geotechnical engineer: Geomechanics
Construction manager: PJ Dick, pjdick.com
Landscape architect: La Quatra Bonci Associates, laquatrabonci.com
Lighting designer: Studio I Architectural Lighting, studioilighting.com; Fisher Marantz Stone, fmsp.com
Owner's rep for sustainability: Paladino and Company, paladinoandco.com