In a typical high rise, the only way to get rid of stale office air is by pumping air in and out through an energy-intensive ventilation system. If you're encased in glass and steel, you can't just open a window. A new office tower does things differently: When the temperature is right, the whole building breathes.
"When we started this project, we aimed at being the greenest skyrise in the world," says Mike Gilmore, director of design and construction services for PNC, which opened the new building, designed by Gensler, as part of its Pittsburgh headquarters. One part of being more sustainable was designing a natural ventilation system that would stretch up all 33 stories.
A double-layered facade wraps all the way around the building, with outer windows that automatically pop open when they sense that temperature and humidity are at the right level and air pollution is low. Inside, vents flop open to let in fresh air. On warm days, a solar chimney—heated by sun on the roof—opens up, and sucks hot air out of the building.
"After the poppers pop and the floppers flop and louvers open . . . the stack effect takes the heat out with zero energy," says Gilmore.
In the winter, the roof collects heat and sends it through the building through a system of fans. The double-skin facade traps almost three feet of air between each layer, helping insulate the building and reduce the need for heating or cooling.
The natural system works quickly, as the team saw on a recent visit just before the building opened. "It was pretty warm because everything was closed," says Benson Gabler, who manages corporate sustainability. "We kind of overrode the system to open the facade, and all of the sudden the natural ventilation mode kicked in, and it just instantly cooled down the floor."
The building is also covered with blinds that automatically open and close to let in the sun and block out heat. Ninety-two percent of the office space gets natural light, and artificial lights don't switch on unless sensors detect that it's truly dim inside.
To save water, an on-site water treatment plant—like a miniature version of the kind that provides cities with drinking water—treats rainwater and recycled water from the building for reuse in flushing toilets, water gardens, and cooling building systems. By catching rainwater, the building helps Pittsburgh deal with a common problem during storms: If it rains too much, sewers often overflow into local rivers, polluting natural habitats.
PNC started experimenting with greener buildings more than a decade ago and quickly realized that building more sustainably didn't actually cost more than the conventional methods. The company now has more than 250 LEED-certified projects in the U.S., more, it says, than any other company in the world. The office tower in Pittsburgh is expected to exceed LEED Platinum, the highest rating for sustainability.
The next step: Teaching employees how to use the new office to make the most of its green features. "While we can design and construct a sustainable building, the actual performance is dependent on human behavior," says Gabler. So far, 140 people have signed up for training sessions on how the building works. "We want to get them educated and excited about the building so they could then share that with their colleagues to really create a culture of sustainability."