In many ways, the Twelve | West building in downtown Portland, Ore., is about energyits generation, conservation, and participationon a district scale. But the energy that drove the 23-story project was a desire to bring new life to a neglected area of the city core. For local project designers Zimmer Gunsul Frasca Architects (ZGF), the solution lay in transparency.

“We wanted Twelve | West to be an urban catalyst that bridged a major thoroughfare to the vibrant aesthetic of Portland’s Pearl District,” explains ZGF principal John Breshears. ZGF’s interest in the project’s success was personal. The company occupies four floors inside the 550,000-square-foot structure, which also includes 17 stories of apartments, five levels of below-grade parking, and three roof-level terraces and gardens. “By making the building transparent, we could reveal the vitality inside,” Breshears says, “but transparency and sustainable performance can be in direct conflict with each other.” In order to resolve the competing goals of visual openness and environmental stewardship, the designers first sought to optimize the mechanical systems.

The team employed computer modeling and design predictions to control lighting in the space and worked with a local curtain-wall fabricator to find the exact glass needed to control thermal gain. ZGFs office space is served by underfloor air distribution and overhead passive chilled beams that cool the space through a natural convention loop, as well as heat recovery at the air handling units and demand-driven airflow control. The team also exposed the concrete ceilings and structure, which provide thermal mass to moderate temperature swings. In the apartments, the HVAC system includes extremely efficient motors and equipment, and a district utility in the Pearl District extended its service area to provide chilled water for Twelve | West.

On the top of the building, four wind turbines serve as an open-air experiment on wind power generation in an urban environment and are projected to produce nearly 10,000 kWh per year, enough electricity to offset that used by the building’s elevators. More renewable power comes from 1,360 square feet of flat-plate solar hot-water panels on the roof, which provide 24 percent of the energy needed to heat the domestic hot water in the building. Energy models predict that Twelve | West will exceed current 2030 Challenge benchmarks for energy use and achieve a 46 percent savings over code baseline.

Breshears says that project materials for the office space were painstakingly researched, and low-emitting materials and finishes were used throughout the building. In the office lobby, white metal ceiling panels are coated with a water-based, solvent-free finish that was not available from the panel manufacturer, so the designers paired two companies together to create the custom product. Recycled materials include 100 percent corn-fiber curtains, linoleum flooring, recycled-denim insulation, and 96 percent recycled, locally manufactured gypsum wallboard. Locally sourced concrete and natural materials also were specified throughout the building.

More than half of the wood used in the office space is Forest Stewardship Council certified. The designers selected bamboo for veneers on doors, casework, flooring, and cabinets, and the office lobby’s wood siding was salvaged from an old trolley barn. An artist crafted the reception desk from wood salvaged from a 270-year-old walnut tree that was felled in Salem, Ore., because it was diseased. One lobby wall showcases a collection of old photographic slides of past projects that were mounted and backlit to create a portfolio display.

Twelve | West’s vegetated roof contains an unusually deep plant medium of 18 to 24 inches, which allowed the team to incorporate plants that will grow tall, some up to 20 feet, to create a lush garden. The deeper substrate also offers a substantial stormwater benefit. Excess rainwater is collected in a 23,000-gallon tank. Combined with cooling coil condensate in the summer months, the rainwater provides all of the project’s irrigation needs and approximately 90 percent of the offices’ toilet flushing needs. In response to the amount of waste diverted from the local sewer system, the city of Portland agreed to offset system development charges for the stormwater retention system, offsetting 91 percent of the system’s total cost, and the system saves a projected 286,225 gallons of potable water annually.

Opened in 2009, the project achieved two LEED Platinum certifications, one under LEED for New Construction and another under LEED for Commercial Interiors for the office floors. At press time, a comprehensive energy performance review was being conducted, as well as metering of the building’s overall energy use and submetering of the office lighting and plug loads, total domestic hot-water use, heating, cooling, and electrical use in the residences. In addition, the wind resources and energy production will be measured by ZGF in conjunction with outside partners, including the building’s construction manager, electrical and mechanical engineer, and the National Wind Technology Center, for five years against predictions. Similarly, researchers at the Center for the Built Environment at the University of California at Berkeley, have partnered with the design team to study glare, daylighting controls, and roller-blind effectiveness to better understand the impact of the high-transparency façade on both occupants and energy use. “We’re benchmarking our energy performance and we launched a measurement and verification plan,” Breshears says. “We want to share what we’ve learned with others to promote more sustainable buildings everywhere.”

KJ Fields writes about sustainability and architecture from Portland, Ore.