AIA/COTE Top Ten Green Projects

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The Plaza at PPL Center

In this photograph, the Plaza at PPL is lit up at nighttime.
Photo credit: Peter Aaron - Esto


  • Location: Allentown, PA
  • Building type(s): Commercial office, Retail
  • New construction
  • 280,000 ft2 (26,000 m2)
  • Project scope: 8-story building
  • Urban setting
  • Completed July 2003
  • Rating: U.S. Green Building Council LEED-NC, v.2/v.2.1--Level: Gold (40 points)

The Plaza at PPL Center, an urban office building, was designed and built in 18 months on a suburban real-estate budget. Located in the center of Allentown, Pennsylvania, this eight-story building is the first new downtown office development in more than 25 years and represents a major commitment to the City by the building's tenant, the PPL Corporation, a regional energy company. While the PPL Corporation occupies most of the building, the owner, Liberty Property Trust, developed one floor as speculative office space, and the plaza level of the building includes retail storefronts.

Chosen as an AIA Top Ten Green Project for 2004. The Plaza at PPL Center was designed by Robert A.M. Stern Architects in association with Kendall/Heaton Associates with support from environmental building consultant Atelier Ten. Additional project team members are listed on the "Process" screen.

Environmental Aspects

Located in downtown Allentown on a previously-developed site, the building sits at a major public transportation node and forms a new public plaza at one end of the City's main business corridor. The highly transparent south façade animates the street scene and metaphorically opens to public view the activity inside. The building is a catalyst for economic development in the center of Allentown's business district.

A dramatic eight-story central glass atrium brings natural light deep into the core of the building, while extensive perimeter glazing provides abundant daylight to, and views from, all building spaces.

Carbon dioxide sensors insure that fresh air is supplied to each building area as needed, and zero-emitting or low-VOC paints, adhesives, sealants, carpet, and composite wood were used throughout. Two two-story, plant-filled winter gardens along the south façade of the building provide unique workspaces, bring daylight deeper into the floor plates, control glare, and improve indoor air quality.

The design integrates environmental moderation and control into the fabric of the building with high-performance glazing, brises-soleil, and a vegetated roof. The building's energy demand is more than 30% lower than code requirements, its water use is 45% below code requirements, and its construction materials contain over 20% recycled content.

Owner & Occupancy

  • Owned by Liberty Property Trust, Corporation, for-profit
  • Occupants: Corporation, for-profit
  • Typically occupied by 800 people, 40 hours per person per week; and 100 visitors per week, 2 hours per visitor per week

Building Programs

Indoor Spaces:

Circulation, Office, Retail general, Mechanical systems, Electrical systems, Conference, Lobby/reception, Restrooms

Outdoor Spaces:

Patio/hardscape, Drives/roadway, Garden—decorative


Integrated team, Green framework, Transportation benefits, Drought-tolerant landscaping, Glazing, Passive solar, HVAC, Lighting control and daylight harvesting, Efficient lighting, Durability, Recycled materials, Local materials, Certified wood, Occupant recycling, Connection to outdoors, Daylighting, Ventilation effectiveness, Low-emitting materials, Indoor air quality monitoring

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Last updated: 4/22/2004

Our thanks to the ENERGY STAR program of the U.S. Environmental Protection Agency, and to the U.S. Department of Energy, and to BuildingGreen, Inc. for hosting the submission and judging forms.

For more information about the AIA/COTE Top Ten Green Projects, contact AIA/COTE. For help on how to use this Web site, contact .

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