Glaziers delight: Scrim walls, like those on Caltrans headquarters, are multifunctional
From drive-up windows to drive-
Located smack-dab in the middle of the metro area’s civic center and kitty-corner from City Hall, the 13-story, 1.2-million-square-foot behemoth rests on a site commanding an entire city block and boasts 760,000 square feet of office space for 1,800 employees. It includes a 3,000-square-foot public lobby, 410,000 square feet of parking for 1,142 vehicles and a vehicle repair shop for the Caltrans fleet. Yet at 430 feet long, 200 feet high and ranging from 300 to 330 feet wide, this narrow slab of a building occupies only a third of its full-block site. It is this building—and not a highway—that marks the single largest construction project undertaken by Caltrans.
Mayne, who recently re-ceived the Pritzker Architecture Prize, beat tough worldwide competition to secure the first-ever design contract from the state’s Design Excellence Program. Built on a fast-track, 30-month schedule from start to finish, the L-shaped facility opened
The building’s blue-gray coated perforated aluminum sheath or skin, also referred to as a system of scrim walls, is its most distinctive feature. The scrim walls are not weatherproof and hang on metal brackets 1 foot away from the glass curtain wall. The system contains three different perforated aluminum panels—1⁄4-inch holes on 11⁄32 centers, 1⁄2-inch holes on 11⁄16 centers and 1-inch holes on 13⁄8 centers—engineered, fabricated and painted by Sierra Aluminum Architectural in
The traditional glass curtain wall contains 1-inch insulating glass units of PPG Industries’ clear Solar-ban 60, with the low-emissivity coating on the second surface, and with all outboard glass heat strengthened. Some glass is as large as 711⁄8-by-1257⁄8 inches. ACI Distribution of Dallas fabricated the glass. The units were structurally glazed to a unitized aluminum curtain-wall system manufactured by Accura Systems Inc. of
The scrim walls were installed about a foot from the primary exterior façade walls and were covered with a base-polymer rolled roofing membrane called Sarnfil. All drafting, engineering, modeling, extrusions, painting and subassembly were performed by Sierra Aluminum Architectural.
Elsewhere in the building, Accura’s skylights comprised 9⁄16-inch laminated glass. The custom sign box had 9⁄16-inch custom silk-screen glass with various names, the state seal, Caltrans and the Caltrans mission statement provided by Goldray Industries Ltd. of
Parts of the curtain wall are coated with the dark gray Sarnafil waterproofing membrane to create the building’s primary weather barrier. Twelve-inch round steel pipes support the skin structure.
The secondary aluminum sheath serves as a sunshade and creates a microclimate in the area exterior to the curtain wall. The façade’s temperature is reduced by this microclimate, as hot air is directed upwards and cooler air rises from beneath. Near ground level, the building’s metal skin peels up to form a canopy that wraps around the adjacent plaza’s edges, drawing pedestrian traffic into the building and thus promoting Mayne’s intent to increase and improve urban integration.
Morphosis first employed the aluminum sheath technique at the Suntower in
Panels open, close on command
On the Caltrans building’s east and west façades, some of the three-dimensional panels that comprise the aluminum sheath serve a primarily aesthetic purpose and remain fixed in place, while more than 1,000 others open and close automatically via a computer program. The program is set to respond to the sun’s position and outside temperatures, regulating heat and sunlight while providing surface variety on the façade. When open, the panels, smaller than the panes constituting the building’s horizontal strip ribbon windows, form a 90-degree angle with the façade. Additionally, even in a closed position, the panels allow office workers changing views of the city by way of the ribbon windows looking onto the surrounding streets of First, Second,
At first, state officials hesitated to equip the building with a mechanical system to regulate the sheath’s panels, but by using stainless steel actuator parts and a pneumatic system, rather than an electrical one, the design-build team was able to persuade its client to follow course. This was after extensive testing of at least five mock-ups, including a full-size version subjected to wind, rain and seismic movement.
Model Glass Co., a contract glazier and fabricator in
As they surveyed the building, Walker and Wells laid out points every 3 feet of the 716,200-square-foot building to determine where the anchor points would go. To mark the points, Wells, in a full safety harness and tied off, had to shimmy down one of the scrim’s supporting steel pipes and up another while holding on with his legs. It was a difficult and rare feat because the steel pipes were heated up in the sun. “Access was so hard in certain parts of that scrim, there was really no other way of doing it,” said Don Farrar, vice president of Model Glass. “But the scrim provides a lot of benefits to the occupants of the building. It gives them a shade means they can control. [It] makes a lot of sense because in this day and age, most owners want glass with high light transmission, but with that you also have a lot of heat gain. The scrim just makes [the glass] perform even better. It’s terrific.”
On the south wall, a series of photovoltaic cells generate an electric output of 92 kilowatts or 5 percent of the building’s energy requirement, contributing to the building’s overall sustainability. Additionally, the aluminum sheath reduces power consumption by about 20 percent and solar heat gain by 15 percent. Two light wells, 30-foot square glass openings in the middle of the building that span the building’s height, allow natural light to reach the interior sections of the facility. The skylights, containing 3⁄8-inch glass, allow office dwellers to reduce use of overhead lighting, thereby cutting down on electricity consumption. In all, the state has reportedly recouped more than $660,000 through programs that reimburse projects relying on renewable energy sources. The Leadership in Energy and Environmental Design program of the U.S. Green Building Council has subsequently given the building a silver rating.
“The high-tech sun-screening device … varies with the hours and seasons, imparting a chameleon-like character to the building that some find unnerving,” wrote contributor Martin Filler in the February issue of House & Garden magazine. “I consider it fascinating. Most modern architecture can be summed up in a minute, but the Caltrans headquarters takes several hours to appreciate fully. … To watch the west façade metamorphose from ethereal translucence in late afternoon to glowing transparency in early evening is a thrilling, almost cinematic experience. The dull gray exterior becomes silvery in the fading daylight as it slowly and steadily unfolds like some exotic flower in a
Both Architectural Record and House & Garden magazines have praised the Caltrans District 7 Headquarters. It was ranked with the best of
However, the building also garners criticism. Some locals deride the mammoth exterior, calling it the “death star” or “battleship.” In a
“You have to wonder if Mayne is using the Caltrans design to offer a critique of gray, faceless bureaucracy—in other words, if he is making fun of his own client, which isn’t exactly beloved by Californians or known for its accessibility,”
Additionally, some office workers complain that when sitting at desks placed fewer than 10 feet away from the aluminum screening system, the resulting perforated pattern on the screen plays tricks on the eyes, causing them to see moiré patterns when they look outside.
Getov argues that any criticism the building has received has been minimal. “The overwhelming majority of the users like the building,” he says. “Nobody will deny that the building has had a huge impact on downtown. On an urban level, we wanted to serve the public to the degree it would revitalize downtown—and we feel we have.”