Wind Steals the Spotlight: Rooftop turbines draw attention to this new mixed-use high-rise in Portland, but itís the less visible systems and design choices that make it a beacon of green.
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Twelve West is best known in the neighborhood for its four rooftop wind turbines but, as developer Dennis Wilde of Gerding Edlen Development points out, those “are just a bit of frosting.” The more meaningful green strategy of this building is not so easy to see. That’s partly because it’s hidden inside the walls and systems, with predicted savings of nearly 50 percent in both energy and water use. Also less obvious is how the project revitalizes its surroundings.
A classic example of urban mixed-use development, Twelve West has retail spaces on the ground floor; an architectural office for the building’s designers, Zimmer Gunsul Frasca Architects (ZGF), on the next four floors; then 17 floors of apartments topped by roof decks; and five levels of parking below the building. It has become an instant anchor for the West End, an up-and-coming neighborhood between Portland’s flourishing Pearl District and its central business area. Thanks to this project, chilled water from Portland’s district cooling system is now available in this part of town.
Sandwiched between the roof decks and wind turbines are vegetated areas and 1,360 square feet of solar hot water panels, which produce about 24 percent of the tower’s domestic hot water needs (and more than 15 times as much energy as the turbines). The 6,000-square-foot roof garden is irrigated with stored rainwater from an oversized fire-suppression tank in the underground garage that also provides for 90 percent of the office’s toilet-flushing needs. (Oregon health codes didn’t allow for use of reclaimed water in the apartments.)
That rainwater reclamation system almost didn’t make the cut, according to Wilde, until the city agreed to a 30 percent reduction in systems development charges based on the anticipated reduction in stormwater runoff. That $205,000 savings brought the simple payback on the water reuse system to about nine years, and allowed Twelve West to help solve Portland’s combined sewer overflow problem. The owners are still on the hook to prove that this system reduces runoff, however, as the city can reverse that gift if they don’t.
Those high-profile turbines supply a tiny fraction of the building’s projected energy load, yet they were a labor of love for the designers, who spent untold hours over two-and-a-half years figuring out how to make them work, even after learning that their contribution would be minimal. Working with turbine manufacturers and leading wind energy experts, ZGF architects Craig Briscoe and John Breshears discovered how little is known about what it takes to make rooftop turbines successful.
As the only high-rise-mounted turbines in the U.S., this installation has already become a key testing ground and scientists will begin analyzing their performance data this summer. One result that is already clear, however, is that “the real world performance of the turbine array has been stellar in terms of noise and vibration,” says Briscoe. Managing those concerns was another aspect of their research, and it led them to the SkyStream (relatively quiet turbines) and to isolation pad specialists in New Jersey for help in minimizing vibration transfer through the base of the masts. In spite of all that effort, “you never know if you’ve been really successful acoustically until you get to measure the actual sound and vibration with those subjective but sensitive instruments that we call ‘occupants,’ ” notes Briscoe.
Significant energy savings are predicted, in spite of floor-to-ceiling glazing in the architectural offices and apartments, notes Breshears, a decision that was driven largely by marketing demands to maximize the visibility of the firm. Wilde agrees and points out that in the apartments the glass walls actually make people uncomfortable: “It looks bitchin’ cool in the photos, but once you move in it’s more congenial to have higher sills.”
Of all the challenges, perhaps trickiest was having the firm as its own client, notes Breshears. “There were definitely too many chefs in the kitchen.” They did enjoy subjecting themselves to the sort of creative exploration usuallly reserved for clients, with a firm-wide meeting devoted to answering questions like: “If ZGF were an animal, what animal would it be?” After that meeting, however, the core design group had to be isolated from the rest of the firm and allowed to work. Underfloor air, chilled beams at the perimeter, and a dearth of finish materials all contributed to the results.
Financially, the project is an unmitigated success, with apartments leasing ahead of projections and two retail spaces leased and under construction. The entire building is LEED Platinum, and the architects anticipate achieving a platinum rating for their interior fit-out as well. Perhaps more importantly, both residents and architects are happy with their space, according to Breshears. Unlike their old offices, the new ones are “light-filled, not glarey, spacious, and comfortable,” he says, adding: “Conversations and interactions are happening now that wouldn’t have happened in our old, cramped space. And that’s changing how we do our jobs.”