The Plaza at PPL Center

File Type: Free Content, Case study
Release Date: January 2005
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The Plaza at PPL Center

Fast Facts

Address: Allentown, Pennsylvania
Company/Developer: Liberty Property Trust
General Contractor: L.D. Driscoll Company
Property Type: Office
Square Feet: 252,193 square feet
Height: 8 stories

Building Description: Liberty Property Trust’s office development for PPL Corporation, designed by Robert A. M. Stern Architects, showcases environmental features that save water and energy, minimize the impact on the environment and provide an inspiring, healthy workplace for PPL’s 600 employees.


Winner of the AIA/COTE Top Ten Green Projects in 2004, NESEA’s 2004 Green Building Award for Large Buildings and the Urban Land Institute’s 2004 Award for Excellence, this urban redevelopment project makes good on the concept “Build tall instead of sprawl.” It uses only 1.7 acres for 252,193 square feet of rentable space.

This LEED Gold certified building is the first privately owned building in Pennsylvania to achieve that status. The building’s green design elements include a dramatic eightstory central glass atrium to bring natural light deep into the core of the building, a transparent south facade with two two-story winter gardens to bring additional light into the floor plates, CO2 sensors to ensure fresh air throughout the building and a public plaza with fountains and reflecting pool that have become a community gathering center.

The Plaza at PPL Center is the new headquarters to Allentown’s largest business, PPL Corporation. PPL Corporation commissioned Liberty Property Trust to develop the project on a site designated as a Keystone Opportunity Zone. Since opening, the Plaza has been a catalyst for economic development in Allentown’s business district.

Urban Redevelopment as a Win-Win Option

The City of Allentown was delighted to keep its largest business in the city and see revitalization of its west end. PPL Corporation and other tenants in the building receive tax incentives for their site selection. And Liberty Property Trust is earning an initial development yield of 11.3 percent on development costs of $60,686,000. At full occupancy, the stabilized yield is projected to be 12 percent. Building green costs about $104 per rentable square foot for the building core and shell construction—a 1.5 percent premium over traditional construction.

Green Features

Sustainable Sites

  • Accessibility to major public transportation.
  • Existing parking garage retrofitted with electric vehicle recharge stations.
  • Bicycle storage and changing rooms for five percent of building occupants.
  • Vegetated roof and filtered storm water that removes 80 percent of suspended solids.
  • Highly reflective roofing and shading of more than 30 percent of hardscape surfaces reduces heat islands.
lobby of The Plaza at PPL Center

Lobby. Photography by Peter Aaron-Esto

Indoor Environmental Quality

  • CO2 sensors in every room and an enthalpy recovery wheel supplemented by humidification control to ensure high thermal comfort levels.
  • Low-emitting materials used for paints, carpets, adhesives, sealants and composite wood paneling.
  • Use of green cleaning products.
  • Eight-story central glass atrium brings in natural light.
  • More than 90 percent of all regularly occupied space on office floors has direct line of sight to an outside window.
  • Indoor gardens bring in daylight, control glare and improve indoor air quality.
  • Individual temperature and light controls for individual offices.

Water Efficiency

  • Landscape vegetation selected to thrive on rainwater only.
  • Vegetated roof and landscape reduce site permeability by just over 15 percent.
  • Low-flow fixtures and waterless urinals to reduce water use by 45 percent, compared with typical buildings.
The Plaza at PPL Center winter garden

Winter garden

Energy and Atmosphere

  • Energy system designed to exceed standard by more than 30 percent.
  • HCFC- and halon-free HVAC equipment.
  • Solar control through Bris Soleils and canopies.
  • Ice storage tanks that reduce chiller sizes by nearly 50 percent.
  • Photometric sensors and occupancy sensors.
  • An environmentally-friendly central cooling system that is 25 percent more efficient than traditional systems and includes a two-mile-long network of pipes that deliver chilled water from a 50,000-square-foot cooling plant.
  • Zero use of CFC-based refrigerants.
  • An HVAC system that includes cooling towers and pumps at the roof level, with a self-contained air-handling unit on each floor.

Materials and Resources

  • More than 20 percent of building material recycled.
  • More than 90 percent of construction, demolition and land clearing debris recycled.
  • About 25 percent of building materials manufactured within 500 miles of the building.
  • More than 85 percent of wood-based material from sustainably managed forests.