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CASE STUDY:
Alley24

Seattle, Washington

A New Face for Seattle: A LEED-certified speculative development in seattle is both environmentally and economically sustainable

By Sebastian Howard

An agglutinative mixed-use development stands quartered by alleys in Seattle’s South Lake Union neighborhood. The building testifies to the city’s changing character. It is at once massive and unobtrusive, a giant with a birdlike appetite. The project comprises 354,000 square feet, including 172 residences and 180,000 square feet of offices, all squatting above 28,000 square feet of retail shops at grade. Using integrated design, architects NBBJ and developer Vulcan Realty have created one of the first LEED-certified speculative properties in the country: Alley24.

Alley24. Seattle, Washington
Photo © Benjamin Benschneider
Alley24. Seattle, Washington


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KEY PARAMETERS
LOCATION: Seattle, WA (isthmus between Puget Sound and Lake Washington)

GROSS SQUARE FOOTAGE: 354,000 ft2 (32,887 m2 )

COMPLETED: May 2007

ANNUAL PURCHASED ENERGY USE (BASED ON UTILITY BILLS FOR ALLEY24 EAST): 48 kBtu / ft2 (715 MJ / m2), 49% Reduction from National Average

ANNUAL CARBON FOOTPRINT (PREDICTED): 13 lbs. CO2 / ft2 (64 kg CO2 / m2)

PROGRAM: Offices, Retail Shops, Residential Apartments

LEED-CI Version 2 Gold

LEED-NC Version 2 Platinum

Sky Conditions   Temp./Dew Points   Heating/Cooling Degree Days
Sky Conditions   Temp./Dew Points   Heating/Cooling Degree Days

TEAM
OWNER: Vulcan and PEMCO Mutual Insurance
ARCHITECT: NBBJ
INTERIOR DESIGNER: NBBJ, Skanska, Robin Freeman Interior Design, Gensler LANDSCAPE: Murase
ENGINEERS: Magnusson Klemencic (structural), Flack + Kurtz (mechanical), Sparling (acoustical)
ENVIRONMENTAL CONSULTANT: Egis Certified
GENERAL CONTRACTOR: Skanska (commercial), Compass Construction (residential), Lease Crutcher Lewis (concrete and historic rehab)

SOURCES
EXTERIOR CLADDING: Rainscreen by Richlite
PAINTS: Sherwin-Williams Harmony Latex (zero VOC)
STAIR TREADS: Yemm + Hart tire veneer
CORK/RUBBER FLOORING:
Expanco
ACOUSTICAL CEILING TILE: Armstrong
FURNISHING: 41% reused furniture
TABLES, ARENA SEATING, KEYBOARD TRAY MOUNTS: dTank
LIGHTING CONTROLS: Lutron
HVAC CONTROLS: Siemens, GreenHeck VCDR-53, Trox Technik

Rising between one and six stories where it meets the property line, the facade is covered with a pastiche of materials. The project’s residential component draws little attention. A mixed-income, Richlite-clad building includes naturally ventilated units varying in size from studios to two-room apartments, and occupancy rates hover just below 100 percent.

The business space, on the other hand, impresses more in terms of both aesthetics and performance. The gunmetal-grey structure contains the LEED-CI Gold offices of Alley24’s contractor, Skanska, and also of the NBBJ, who designed the office interiors. Together, the firms occupy more than half the office space. NBBJ alone leases some 78,000 square feet over three floors. Since opening, the offices have operated very close to the ambitiously low-energy consumption target levels proposed by Architecture 2030, using some 49 percent less energy than the national average.

Alley24 is not formally iconic. NBBJ lead designer Brent Rogers says the team wanted to let the building’s sustainable features influence its appearance “rather than, for instance, an abstract idea about a relationship to a broken electric guitar.” Rogers is referring to Frank Gehry’s whimsical, willful museum, the Experience Music Project, which was commissioned by Microsoft co-founder Paul Allen. Allen’s firm, Vulcan Real Estate, owns around one-third of the land in South Lake Union.

As in so many other neighborhoods in American cities, the urban landscape of South Lake Union is transforming fast. Industrial buildings populated the 60-block urban neighborhood until recently. Lately, those have been replaced by cafes, offices, and boutique stores.

Allen’s firm has helped foment the neighborhood’s rapid change: “We’ve developed everything except industrial, because South Lake Union really isn’t an industrial neighborhood anymore,” says Vulcan spokeswoman Laurie Mason Curran. Alley24 aims to attract what Vulcan’s publicity material calls a “creative class” of designers, architects, and other professionals who work at desks rather than on assembly lines—people who will shop at the neighboring REI flagship store, or the nearby, Vulcan-developed, Whole Foods Market.

Alley24 sits on a full city block jointly owned by Vulcan and Seattle insurance company Pemco. A sprawl of commercial laundry facilities built in the first half of the 20th century initially occupied the property. Their landmarked brick facades have been incorporated into Alley24’s north side, in the residential component. Though the visual play of old and new engages the eye, these brick faces appear as caricature: a clean, ersatz “industrial aesthetic.”

Mark Blatter, director of real estate development at Historic Seattle, a non-profit group that aims to preserve the area’s historic architecture, notesan “undeniable” effect on the setting—its height and footprint dwarf neighboring buildings. For a traditionalist like Blatter, the assimilation of historical facades into an otherwise unequivocally contemporary building is preferable to destruction, but ultimately amounts to little more than lip service.

To the charge that the newer construction includes more environmentally sustainable features than a pre-war warehouse, Blatter counters that conserving energy and preserving history aren’t antithetical: “What people overlook is the value of the embodied energy in an existing structure. That needs to be in the equation somewhere.”

According to Brent Rogers, however, the existing buildings were irreparably decayed by water damage and years of neglect. NBBJ was able to save some of the heavy timber from the laundry buildings and redeploy the beams as structural elements in Alley24’s residential component. But the total quantity of repurposed material ultimately remains low: the U.S. Green Building Council awarded the project no LEED points for either building or material reuse.

In addition to the brick facades, NBBJ had to design around an existing north-south alley bisecting the property. Though it cost valuable floor space to keep the alley running through the block, the cleft neatly delineated the office and residential spaces, and it increased the number of exterior windows possible in both sections.

The design team then added a second alley running perpendicular to the first. This passive, planted space is devoted to foot traffic, lined with retail stores and gardens, and it serves to further break up Alley24’s massing. Both the office and residential lobbies have entrances along the alley: at rush hour, a stream of office employees fills the veins that run to Alley24’s heart.

Under most circumstances, a slim space bordered by six stories of edifice would make a pedestrian feel overwhelmed by the view from the base of a canyon’s looming walls, but Alley24’s namesake feature has enough doorways, landscaping, and material variety that it feels more like what Rogers calls “a narrow European street without the Vespas.”

To grapple with the twin challenges of creating a speculative, sustainable office space, Vulcan engaged mechanical engineers Flack + Kurtz very early in the concept and schematic design phase. Among their charges, advising NBBJ on the placement, orientation, and size of the windows and shading system was paramount. Allan Montpellier, Alley24’s lead mechanical engineer, explains that his firm “worked with the architect to optimize the shape of the building. That was pretty unusual, and it was a great example of integrated design.”

The facade optimization of Alley24 represented a balancing act between admitting daylight and moderating solar-heat gain. “We were very aggressive,” says Rogers, “about keeping the sun from hitting the glass.” The team used several external shading strategies, including fixed aluminum sunscreens and an automated system of blinds that responds to changing environmental conditions. The computer-controlled blinds lower and articulate according to the angle and intensity of the sun—generally deploying on the office’s east facade from sunrise until around 11 am, when they silently retract and the western blinds drop.

These measures resulted in a changing, layered surface, with 30-inch metal fins jutting defiantly from the facade, and motorized blinds that move with the sun. “The elements that are aggressively sustainable,” says Brent Rogers, “also give the facade scale, making it interesting.”

With solar-heat gain effectively mitigated, NBBJ was free to add large, clear windows to the facade, resulting in ample daylighting (despite the comprehensive shading mechanisms, some offices are nearly 90 percent lit by the sun). Electric light fixtures use photocells to automatically turn off when ambient illumination is strong enough to obviate the need for further electric lighting.

In an early design for Alley24, light wells punctured the office building, increasing the number of perimeter walls and therefore, the number of operable windows. The plan would have used only passive ventilation for cooling. But, Montpellier remembers, Vulcan “ended up needing the additional space to make the building pencil out. That created a big problem to solve from an HVAC perspective, because natural ventilation couldn't work at that point.” The solution was one that Flack + Kurtz had advocated from the beginning: raised-floor ventilation.

This scheme has the virtue of being both flexible—each occupant controls the workspace airflow—and low-pressure, so that less fan energy is needed to circulate air through the plenum. Both factors help conserve energy. An under-floor ventilation system also quelled the fears of prospective tenants who were skeptical of passive-ventilation’s efficacy (implementing tenant submetering ensured occupants consuming less energy that they would not have to subsidize those using conventional HVAC only). “So where we lost the light well,” Montpellier explains, “we gained the raised floor. It solved a lot of problems.”

When external temperatures range between 62 and 72 degrees, tenants receive notification, via an email or a green light, to turn off the mechanical air conditioning and open perimeter windows. The system is simple, effective, and employees generally favor it. “People are literally clapping and cheering in NBBJ’s office when the green light comes on for the first time all season,” Montpellier says. The appeal of fresh air—and the noticeably lower energy bills—convinced even once-hesitant tenants to use passive ventilation.

Flack + Kurtz’s work in Alley24 was influenced by Vivian Loftness, a Carnegie Mellon professor of architecture known for compiling compelling data that shows a strong correlation between quality of the work environment and health and productivity of workers. Loftness champions the use of operable windows, daylighting, underfloor air, mixed-mode HVAC, and low-VOC paints—all measures used in Alley24.

Such tactics produce quantifiable benefits. Skanska, for example, reports that productivity has increased since the firm moved to the facility, and that employee sick days are down by 30 percent. According to Montpellier, Alley24’s occupants have a “definite effect on the energy performance of the building” by complying with the alerts to open and close the windows according to external temperatures.

The mixed-mode HVAC system provides, of course, more than an employee palliative. CBRE, Alley24’s facilities manager, reported that Alley24 achieved a 49 percent reduction in energy consumption in its first year of operation. The success of the mixed-mode ventilation system offers evidence that integrated green design often provides better results than simple energy-saving techniques.

The fact that Alley24 operates just shy of the Architecture 2030 energy-use goal encourages Allan Montpellier. “The challenge is to get to 50 percent or below the CBECS baseline, and we're essentially there." Perhaps more significant are the implications of Alley24’s commercial success. With some 96 percent of residential units and all of the office space occupied, Montepellier thinks, “a speculative office building developer could try to make the next step” and develop a 100 percent passively ventilated speculative office space.

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This article appeared in the March 2009 print issue of GreenSource Magazine.

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