By C.C. Sullivan
As American architects become better at integrating new technologies into their projects, U.S. buildings are becoming more energy-efficient than ever. A few states, like California and Massachusetts, already have rigorous energy codes in place; new buildings that best those rules represent a serious accomplishment. But when projects on American soil win awards for energy efficiency in Europe, where regulation and public scrutiny are far tougher, green-minded designers everywhere stand up and take note.
A useful case study is the San Francisco Federal Building, a quirky and unpretentiously innovative sliver of offices on Mission Street. Operating largely without mechanical cooling and with limited electrical lighting, this unusual facility consumes about half as much power as a conventional office occupancy of the same size. (These features and facts helped earn it the first international Zumtobel Group Award for Sustainability and Humanity in the Built Environment in late June, sponsored by the lighting company.)
Yes, it's outlandishly green. Yet energy consumption is a mere sidebar in the eyes of Thom Mayne, the Pritzker Prize-winning architect and principal of Santa Monica, CA-based Morphosis. This big idea is its rethinking of the U.S. office environment.
"We looked at the culture of the workplace and the generic nature of the American office building and questioned the whole idea. Then we looked for ways to break down the balkanizing that occurs in our typically big workspaces," says Mayne. Some of those performance-driven advances can be seen in the structure's outward form - "We squeezed the building to a very narrow floor plate," says the architect - while others are only hinted at by the fenestration patterns. For example, Mayne employs skip-stop elevators, which compel workers to use the stairs and lobbies more frequently, as well as open, studio-like spaces with fewer enclosed offices and workstation walls.
"We're promoting different levels of working and meeting spaces. That's the essence of build
ing," says Mayne. "Occupants can see the views of the city on one side and Mission Bay on the other. But more important, it promotes a very nonhierarchical environment, and that was a very important part of the program from early on."
Stealthy Revolution in Design
Architects who have worked for federal agencies might think it unlikely that a government client would volunteer for a quasi-experimental exercise in workplace planning. But such is the case for many Morphosis clients, who by hiring the firm become part of a stealthy revolution in building design.
Also unexpected is the physical relationship of this new complex and its host city. Dominating the mass of the San Francisco Federal Building is a long, 18-story glass and perforated metal office tower, 240 feet high and 320 feet long - but a mere 60 feet wide - used exclusively by federal employees. It stands behind a large public plaza, partially covered by perforated metal sunshades and flanked by a sculptural, 3,000-square-foot cafeteria structure. Across the plaza stands an outbuilding expressly made for public visitors doing business with the tenants, which include the Department of Labor and the Social Security Administration. This functional division, and the large plaza with its sculptural bollards, enhances security for its attack-wary occupants.
The desire for using exclusively natural ventilation drove the site massing and the shape of the narrow midrise office block, says Tim Christ, project manager and principal of Morphosis. "The GSA (General Services Administration) was very cautious and wanted us to be conservative and make sure it worked" without mechanical cooling, he explains. "We used rules-of-thumb for the depth of the floor plate to enhance natural ventilation and rules-of-thumb for daylighting by means of a full-height curtain wall."
The firm's design guidelines were adapted from strict European codes the architects first studied for works such as the 2002 Hypo Alpe Adria Center in Klagenfurt, Austria, where codes require that workers' offices be no more than 25 feet from a window. "Also, you can't really effectively do cross-ventilation in a building wider than 70 feet, so we kept it to 60 feet," says Christ, adding that the information the design team used is readily available to anyone.
To ensure the building would be comfortable, fully functional, and sustainable, Morphosis oriented the façades and patterned the fenestration to capture prevailing northwest sea breezes. The team also explored future development patterns in the area: Would new towers obstruct the building's lifeblood wind? Testing in a wind-tunnel lab helped the design team estimate pressures on the main enclosure. Then the architects collaborated intensively with several key consultants over the course of about a year to fully model the ventilation scheme. Besides engineers from Arup, the firm tapped experts at Lawrence Berkeley National Laboratory and the University of California at San Diego (UCSD) for peer review of the engineering plans. To analyze ventilation, UCSD employed computational fluid dynamics, or CFD, to visualize bulk airflow and daytime interior temperatures.
Inside the office spaces, exposed concrete ceilings, columns, and walls provide thermal mass to moderate interior temperatures during the day. A novel cast-in-place floor system, created with specially designed forms, features a fluted surface on the slabs' undersides, enhancing airflow and increasing surface area for thermal exchange. The floor side was customized for the GSA, too, formed with a built-in distribution system for power and communications cabling. High in slag content, the concrete itself is also brighter and more reflective than a typical mix, giving a boost to daylighting effectiveness.
Manually operated windows at desk level ventilate the perimeter office spaces, along with upper vent windows and foot-level trickle vents that are automatically controlled by a BACnet building automation system (BAS) that governs the interior temperature setpoint. Some enclosed private offices have thermostat control via the BAS, as well as occupancy sensors to control lighting. Open office areas use a daylight harvesting system that dims to zero when sufficient natural light is available; subcontrollers in conference rooms and auditoriums allow individual scene selection. To ensure a good level of acoustic privacy, a soundmasking system is integrated into the pendant fixtures throughout the open offices.
Thermodynamic Envelope
As much as the overall shape and interior materials, the building skin required careful design to ensure adequate ventilation, daylighting, and thermal control over a range of expected conditions. As in many other projects conceived by Mayne, a sunscreen protects the east and west exposures from excessive solar gain, this one of perforated stainless steel attached by tube-steel framing to structural concrete. Operable windows and automated ventilation panels respond to changes in weather and interior temperature. The north façade, alternatively, employs fixed translucent glass for shading and diffusing sunlight. To block glare from low sun angles, glass fins enliven the northwestern elevation. These outboard elements obviated the use of interior blinds and shades, which might have compromised daylighting levels and heat gain if left to the control of inattentive occupants.
As Mayne explains, these elements are emblematic of an approach to sustainability that rejects sealed enclosures in favor of "high-performance envelopes." Similar to automated building systems, this is an emerging and important way that buildings can be responsive (and responsible) to the environment.
In addition to automatically opening and closing the vent windows, the BAS operates the sunscreen panels and vision panels based on interior temperature as well as a solar calendar that predicts solar angle and location for the given time of year. This is integrated with a brightness sensor that can override the solar program based on lux levels, in case the sky is overcast or has passing clouds. The sunscreen panels open during any fire alarm mode to help move smoke away from the façade. Last, a weather station provides wind data to the BAS so that panels can be closed when wind speed is high enough to cause a risk of panel deformation.
"We've been playing with these materials and systems for some time in our office," Christ explains. "We integrate formal language and materiality more directly to performance criteria and use elements that are logical thermodynamically."
Still, using novel architectural approaches and cutting-edge green concepts such as natural ventilation, thermal mass storage, and active sunshading demanded equally sophisticated design methods. Beyond their team of seasoned consultants - and the lab tools like wind tunnels and CFD - Morphosis shepherded the design process through building information modeling (BIM). The 3-D model helped coordinate the complex building geometry with engineers, manage production of construction documents (CDs), and calculate rough cost estimates on the fly.
Using the novel BIM approach - and the unusual design elements that resulted - led to tens of millions of dollars in project savings in construction costs and operations. Many of those figures were anticipated and quantified even before groundbreaking (see "Digitizing the Trades").Convincing the Client
Such anticipated savings - and assurances to the GSA that the design was not only best-in-class but pure common sense - were crucial to making the project happen, says Christ. Among the most persuasive cases the building presented are the long-term savings the GSA is enjoying by using natural ventilation - a feature initially mocked in the mainstream press.
Another unusual approach was the electronic signage employed throughout the building for wayfinding and as an occupant directory and in the conference center for occupancy and scheduling. The product enhances productivity directly, integrating information from a 16-screen LCD video wall at the main entry with signage points throughout the interiors, including LED text panels above the doors inside each elevator. Built on an aluminum support frame, the lobby video wall also streams national news and announcements of local events through text, graphics, and video. Overall, this signage network "promotes conversation and communication among building tenants," says Morphosis designer Brandon Welling.
Far trickier than convincing the client about natural ventilation was presenting a strong argument for investing a higher-than-usual proportion of the construction budget into a complex façade system. As Christ notes, such trepidations usually stem from a building owner's concerns about maintaining the exterior elements. Up Mayne's sleeve, however, was a useful response: The mechanical systems would be far less complicated, requiring limited upkeep compared to conventional office buildings. The savings could be reinvested into the skin.
Backing up this assertion were financial projections the GSA could sink its teeth into. "We do a lot of economic modeling simultaneous with our design process, rather than waiting for outside estimators to give you the bad news," says Christ. "It's not the most sexy part of architecture, but as long as you show the client the consequences of each choice, you can be ahead of the game."
C.C. Sullivan ([email protected]) is an author and communications consultant specializing in architecture, design, and building technology.
PRODUCTS USED:
CAD system and BIM: Bentley Microstation, Bentley Structural
Structural system: Auger-cast drilled pile foundation with pile cap load transfer to primary concrete shear walls; wave slabs and upturned beams above
Annex building: Steel structure with east-west moment frame and north-south concentric braced frame. Scrim support is galvanized tube steel and built-up beams with bolted connections
Custom clear anodized-aluminum window wall and perforated stainless-steel sunscreen panels: Permasteelisa Cladding Technologies
Concrete: Exposed high-volume-slag replacement cast-in-place concrete
Built-up roofing: Tremco
Glazing: Viracon (exterior), Oldcastle (interior)
Wood doors: Algoma Hardwood
Acoustical ceilings: Armstrong acoustic panels in offices
Maple cabinetwork and custom woodwork: ISEC
Paints and stains: ICI; Tiger Drylac Powdercoating
Custom printed mesh art panels: Impact Imaging
Fabric wall coverings: Maharam
Fiber-reinforced cement panels: Swisspearl
Perforated maple wall and ceiling panels: 9-Wood
Ground and sealed concrete floors: Perfect Polish
Bathroom floor and wall tile: Daltile
Rubberized flooring and surfacing: Ecofloor
Linoleum flooring: Armstrong
Carpet: Interface
Raised flooring: Tate
Office furniture: Herman Miller
Interior ambient lighting: Zumtobel (pendants and downlights); DelRay (corridor downlights); Contech (MR16 downlights); Artemide (restroom and hallway sconces); Lighting Services (lanterns); Daybrite (office troffers) Lightolier, Prudential (lobby linear lighting)
Exterior lighting: Bega (lanterns and steplights); Paramount (canopy linear): Arrow (neon artwork); Lutron (controls)
Elevators: Mid-American Elevator
Mechanical systems:
Centrifugal chillers with cooling towers, steam purchased from local utility; variable-air-volume system with economizers; underfloor displacement ventilation system with economizers; and natural ventilation cooling with finned tube convector heating elements
Electrical systems:
Busbar distribution system with dedicated bus for mechanical equipment; panel-level monitoring of energy use; daylight harvesting; emergency generator for life-safety element and server shutdown
Plumbing systems:
Split level distribution system with redundant feeds; reduced-flow fixtures throughout; automatic high-rise fire suppression system
Building automation protocols: BACnet
Signage: Ariadne system by ASI Modulex
Acoustical soundmasking system: TOA
Security systems: CCTV throughout site and scanning of visitors and packages at all entries
