Green to the (Structural) Core: A home for environmental and social action is true to the legacy of its namesake
A quick glance at the tenant directory in the lobby of the David Brower Center reveals that the four-story structure in downtown Berkeley, California, is not a typical office building. Names like the Earth Island Institute, the Green Jobs Network, and the Bay Area Open Space Council, give visitors a clue that the 30 organizations occupying the upper floors share a set of common goals—all are focused on social issues and sustainability. “Brower was conceived as a home for environmental action,” explains Amy Tobin, the center’s executive director.
The 43,500-square-foot building’s ground level contains facilities like a 178-seat auditorium and a 1,300-square-foot gallery intended to help its like-minded tenants connect with each other and the surrounding community. It also has an organic restaurant. Brower, completed in the spring of 2009, is part of a larger project that includes a 97-unit affordable apartment building known as Oxford Plaza, retail space, and a below-ground garage. The approximately $75-million mixed-use complex, financed with an array of grants, tax exempt bonds, low-interest loans, and donations, occupies a city-owned plot near the southwest corner of the University of California (UC) Berkeley campus, replacing what was, until the start of construction in 2007, a surface parking lot.
The office building’s namesake, David Brower, a Berkeley native who died in 2000, was the first executive director of the Sierra Club and founder of several other environmental organizations, including the League of Conservation Voters. In keeping with his legacy and the center’s mission, the design team has made the building about as green as they come, with resource-conserving and occupant-friendly features such as renewable power generated on-site, displacement ventilation, and rainwater collection and reuse. Many of these systems are explained and their performance tracked in real time on a dashboard on view in the lobby and on the center’s Web site.
The building, on target for LEED Platinum certification, is more than a checklist of sustainable attributes, however. It is the product of a highly integrated design process, with its constituent parts tightly coordinated, and often contributing to the performance of multiple systems. The most visible example of this integration is a 68- kilowatt photovoltaic (PV) array that wraps around the parapet. In addition to generating electricity (enough to offset about 35 percent of demand in the first year of operation), it serves as an awning, protecting top-floor windows on the south facade from solar gain. As the structure supporting the PVs turns the building’s prow-like corner, it twists, maintaining the optimal orientation for power production and maximum exposure to daylight for north-facing spaces.
Another illustration of the project team’s coordinated approach is the building’s exposed poured-in-place concrete structure. The material was chosen, at least in part, to create a dialogue with the concrete walls of the university’s Art Deco track stadium across the street, according to the center’s architect, Daniel Solomon, FAIA, principal of the San Francisco-based eponymous firm formerly known as WRT-Solomon E.T.C.
The frame isn’t only an architectural expression, it also plays a key role in the energy-efficient mechanical strategy: the concrete’s thermal mass, along with a radiant system embedded in the slabs, provide heating and cooling, while the plenum below the offices’ raised floors serve as the main mode of fresh air distribution.
One especially unusual aspect of the structure is its so-called “self-healing” capability, intended to ensure the building’s longevity, even if it is struck by a powerful earthquake (a likely possibility given that the site is less than a mile from the Hayward Fault). The combination of a vertically post-tensioned core and a pair of horizontally post-tensioned moment frames was devised to allow the structure to flex and move during a temblor, then realign without sustaining permanent deformation. This strategy goes well beyond seismic code requirements, which emphasize preventing loss of life rather than minimizing property damage. “The code is about throwing the building away,” says David Mar, principal of Berkeley-based Tipping Mar, the project’s structural engineer.
Even though LEED contains no credits that pertain to durability, the designers regard it as one of the building’s primary green attributes. They hope that its resiliency will earn points for innovation.
The team has also applied for innovation credits for steps it has taken to reduce the embodied energy normally associated with a concrete structure. To reduce the concrete’s carbon footprint, engineers have used slag (a by-product of steel making) to replace about 70 percent of the portland cement in the foundations and 50 percent in the superstructure. Even though the slag was transported from China and the aggregate from Vancouver, the carbon dioxide emissions from the resulting structure are 45 percent less than they would have been with a conventional mix, according to Mar.
Other strategies, such as Brower’s daylighting, have a more direct effect on the day-to-day experience of occupants. The offices have nearly 100 percent continuous daylighting autonomy—a metric that measures what portion of normal working hours spaces can rely on sunlight alone, says George Loisos, principal of Loisos + Ubbelohde, Alameda, California, the team’s environmental building consultant. Designers accomplished this by pairing relatively narrow offices (about 27-feet-deep) with generous glazing and lightshelves on the south and east elevations. These bounce light into the interior and shield heat gain and glare.
To ensure that existing or future tenants don’t make modifications to their spaces that could alter the quality of the office daylighting, or hinder other aspects of building performance, the developer and property manager, Equity Community Builders, has created fit-out guidelines. These include restrictions on the height of solid partitions that might obstruct sunlight penetration and require that ceilings be painted white for maximum reflectivity. They also limit the area that can be covered with acoustical tile in order to maintain enough exposed surface for optimal functioning of the radiant slabs.
Curiously, most tenants have elected to defer installation of any acoustical treatment, which could explain the low marks the building received for acoustic quality in an occupant survey conducted by the UC Berkeley-based Center for the Built Environment (CBE). Only 18 percent of respondents to the Web-based questionnaire, which asked tenants about various aspects of the indoor environment, were satisfied with Brower’s acoustics.
The design team points out that is not uncommon for green office spaces, which often rely heavily on thermal mass (and therefore many hard and sound-reflective surfaces) and open office layouts, to have less-than-perfect acoustics. On the whole, however, Brower scored well, with 87 percent of participants saying they were generally satisfied with the building, a result that puts it in the 82nd percentile of the approximately 500 projects in the CBE database.
Suzanne Brown, an Equity Community Builders associate who has her own office at Brower, appreciates the building’s connection to the outdoors, the quality of the air, and its minimalist architecture. She also points to the sense of shared purpose among the occupants. Brower “feels like a second home, surrounded by family and friends, all working toward the common goal of a more just and sustainable community.”