The Tower at PNC Plaza, designed by Gensler, is nearing completion in Pittsburgh. The 33-story building is expected to rely on natural ventilation for more than 40 percent of working hours and use only half of the energy of a standard office building.

A squat 1,200-square foot outdoor mock-up erected in a Pittsburgh industrial park is helping PNC Financial Services Group refine The Tower at PNC Plaza, which the company claims will be the world’s greenest skyscraper. Scheduled to open this fall in downtown Pittsburgh, PNC’s new 33-story headquarters, designed by Gensler, is a naturally ventilated highrise with a solar chimney at the core of its trapezoidal floor plate. It is expected to use only 50 percent of the energy of a standard office tower. In a briefing late last month, PNC director of corporate real estate Gary Saulson, along with members of the design team, discussed how data garnered from the module—the largest and most complex built by PNC—have helped tweak the building’s design and operations. Positioned with the same solar orientation as the downtown tower, the mock-up has been used to test the tower’s double-skin facade as well as its automated-blind and lighting systems. The module has also served as a tool for testing the building’s radiant panel technology and its chilled beam system and for evaluating types and placement of custom furniture.

The full-scale mock-up replicates one portion of a typical office floor at the southwestern corner of the transparent building and has sensors that monitor temperature, humidity and light levels. An active double glass skin on the southern wall features a 30-inch cavity, with operable windows, called poppers, on the exterior and doors and adjustable floor-level vents, or floppers, on the interior. A skinny double skin, eight inches deep, covers the western side. Operable blinds are mounted within the cavities on both exposures. A metal catwalk spans the spaces between the exterior and interior panel on the active, south-facing facade.

Dozens of designs for the sliding glass door that will allow office workers to step on to the catwalk were tested for ease of operation. Redesigning the blinds and testing different colors and perforations helped the project team limit heat build-up within the pocket and control glare. A green light in each workspace will indicate when wind and weather conditions are right for occupants to open the catwalk doors.

Saulson said that the building will rely on natural ventilation 42 percent of normal working hours, a boost from the previous estimate of 40 percent. Module data confirmed that during summer months, the building will be able to be naturally ventilated in the early morning hours before employees arrive for work. When temperature, pollution, or pollen levels are too high, mechanical ventilation will kick in. PNC is now studying information collected over the past 18 months from the module and its onsite weather station to adjust building controls and achieve further energy savings.

With the tower’s core and shell now 90 percent complete, PNC expects 2,300 employees to begin moving into the 800,000 square foot building in September. Saulson said the $400 million project, including $280 million in construction costs, is on time and on budget.