San Francisco Public Utilities Commission

San Francisco Public Utilities Commission’s wind turbine support tower features a public art installation that uses tens of thousands of five-inch polycarbonate squares that move freely in the wind.

The San Francisco Public Utilities Commission (SFPUC) is what other cities might refer to as the water and sewer departments. So it makes sense that the municipal unit’s new 13-story administrative structure, completed in 2012, would be exemplary in how it uses its water. Members of the project team, from the architects to the engineers and builders, were strongly driven by a client who was tenacious about exceeding the stringent San Francisco Green Building Code. The team of architects, structural engineers, contractors, subcontractors, and vendors all collaborated to find ways to make the structure LEED Platinum, earthquake resistant, and affordable—three things that don’t come easy.

Teamwork/Collaboration

In the planning stages, city leaders were adamantly fixed on erecting a LEED Platinum structure to serve as a green icon. But the original steel-frame design would overrun its budget by $40 million, so San Francisco-based Webcor Builders worked with its design and engineering partners to devise a vertical post-tensioned concrete frame building that met environmental and seismic goals, enabled an additional floor, and brought the project back on budget. “Everyone worked together, with a goal to build something that honors our Hetch Hetchy Reservoir [the source of San Francisco’s drinking water] and what the Public Utilities Commission does while educating generations to come,” says Brook Mebrahtu, senior project manager for the city’s Department of Public Works. “This project is an example for municipalities across the country.”

Windows and Floors

San Francisco has sunny days 66 percent of the year, so buildings have the opportunities and challenges of incorporating natural daylight into workspaces while trying to counteract the excessive solar heat gain of glazing-heavy envelopes. The architects performed a daylight modeling analysis to guide them in devising a hyper-customized system of double-glazed, fritted windows that vary by pane to account for differences in available daylight (1). Interior window shades and exterior Venetian blinds and light shelves are all coupled with automated light sensors and controls that permit optimal lighting for the building’s occupants while reducing energy demand (2). The concrete floors include an under-floor air cavity for data infrastructure and air distribution, which draw in San Francisco’s famously cool air as a more energy-efficient solution to control thermal comfort (3).

The solar array on the roof, combined with the wind turbines also on the roof, can generate up to 227,000 kilowatt-hours per year.

Solar and Wind

Extensive sunshine translates into 227,000 kilowatt-hours of power collected on rooftop photovoltaic arrays. More visible are the wind turbines situated along a vertical bow on the building’s northern façade, which takes advantage of prevailing north-northwest winds (4). The 5,800 kilowatt-hours generated by the turbines currently supply only a fraction of the building’s electricity needs, but the client looks forward to future opportunities with more efficient turbine technologies. The dramatic, architecturally curved glass façade was designed to increase the wind speeds and max out the efficiency of the turbines. It also makes a strong visible statement about sustainability to local passersby.

The Living Machine

Although SFPUC is in the business of providing water, the building demonstrates several ways that water usage can be reduced by 60 percent over comparable structures through the capture of storm water and by recycling greywater and even blackwater. No potable water is used for landscaping, instead storm water and blackwater are run through the facility’s Living Machine, an on-site wastewater treatment system that mimics the cleansing functions of wetlands. Toilets and urinals also use the water, after it has filtered through biota on the perimeter of the building’s lobby and through a series of tanks and settling chambers. All these features save 2.7 million gallons of water per year.

All of the conference rooms have controllable shading devices to minimize solar heat gain.

Employee Wellness

In all the planning around water and energy conservation and seismic resiliency, the primary function of the building—a place for people to work—was not lost. Far from it, in fact; with 30 percent more fresh air in the building, worker productivity is enhanced. Weather permitting, occupants can open windows, and the use of artificial lighting is minimized when the exterior window shelves bounce indirect light into workspaces (5). An innovative elevator system whisks workers more efficiently to their destination floors, but many skip that altogether by using the stairs (6). And why wouldn’t they? The glass-enclosed staircase features views of the four turbines and a 200-foot polycarbonate art feature that responds to wind. “It’s absolutely stunning,” says Megan White, LEED Webcor Builders’ sustainability manager. “The sunlit, architecturally attractive feature draws more people to using the stairs rather than using energy-powered elevators. It provides a more effective use of egress space while creating a place for interaction among employees.” This nod to human fitness in a pleasant space seems a perfect fit for one of the country’s greenest buildings.