Founded in 1935, the City College of San Francisco (CCSF) is a two-year community college that serves some 90,000 students at various sites around the city. To accommodate growing demand for its services, CCSF expanded by constructing a $47 million Multi-Use Building (MUB) at its main Ocean Avenue campus. The faculty at the college has been jockeying to schedule upcoming classes in the new facility. Bright and airy, the four-level, 100,000-square-foot structure accommodates 1,500 people on a given day. Considering the density, it's all the more impressive to find out that the building is, according to the design team, one of the largest contemporary structures to rely on natural ventilation.
Location San Francisco, California (Cloud Hill)
Gross area 102,391 ft2 (9,512 m2)
Cost $47 million
Date completed Summer 2010
Annual purchased energy use (based on utility bills) 29 kBtu/ft2 (328 MJ/m2), 36% reduction from base case
Annual carbon footprint (predicted) 6 lb CO2/ft2 (30 kg CO2/m2)
Program Classrooms, offices, computer lab, study area, family center, café, meeting rooms
TEAM & SOURCES
Curtain wall Centria MR3-36, Econolap ¾"
EIFS/ACM Swisspearl Reflex Champagne
Windows Kawneer 1600 Series
When you first arrive at the MUB, you can't help but notice how incredibly windy it is. Students walk up snuggled inside their hoodies, a string of red flags outside the café flaps wildly, and piles of leaves swirl in the vestibule just inside the north entrance. High up on a hill, there's nothing to block the MUB from the breezes coming off the Pacific Ocean, 4 miles away.
These strong winds, which can gust at up to 30 miles an hour, were an inspiration to Peter Pfau of San Francisco's Pfau Long Architecture. "When we saw the breezes coming up off the ocean, our first thought was, 'Let's put them to work!' " he says. It cost no more to implement the natural-ventilation system, which combines mechanically controlled louvers with radiant heating and cooling, than a traditional HVAC system. Furthermore, the clever design saved a significant amount of space that would have been required for ductwork and mechanical equipment.
"The central idea was to take a step forward from the brutal efficiency of double-loaded corridors and put an atrium in the building," says Pfau. Atria have long been a popular way to introduce natural light into large structures. But in this case, the atrium plays a significant role in the natural ventilation. On top of the building are a series of 10-foot-tall glass monitors, which are angled away from the ocean. The breezes flow over the top, creating negative pressure on the side facing the hill. This suction augments the natural stack effect and pulls warm air out of the building. In the winter, a radiant floor system warms the space while natural ventilation brings fresh air into the building. Working with local firm Interface Engineering to model the airflow, the architects figured out how many monitors they needed—15 altogether—and what the shape and dimensions should be to take advantage of the prevailing winds.
It was not Pfau's first experience with naturally ventilating a big building; in 2009, he completed a renovation of the 86,000-square-foot San Francisco Friends School. He added thermal towers on each corner, with metal roofs that heat the air and thus accelerate its upward flow. "It's the same concept, where the building is the ventilation system," says Pfau.
The MUB has 35 classrooms, each with louvers along the ceiling on both the exterior wall and the wall facing the atrium, allowing cross-ventilation. Each also has its own temperature controls, so that the louvers open and close automatically in response to carbon-dioxide levels and temperature in that particular room. "Each space is self-handling, instead of having fans and ducts that go long distances—it's more efficient that way," says Pfau. The building even has a full weather station to track temperature, rainfall, and other climatic data, as well as wind sensors. "By putting in enough monitoring systems, we can figure out a way to resolve any problems that come up," says Hormoz Janssens, principal at Interface. "I was expecting to have a lot of issues, but we've actually had less issues here than we've had with most completely mechanical buildings. There's just less stuff that can go wrong."
Because the building is in the chillier climes of Northern California, most of the cooling has been done simply through natural ventilation; artificial cooling has been necessary only twice in the last year and a half. Radiant-floor heating and cooling are both supplied through a ground-loop geothermal system, the city's largest to date, designed to supply five additional future buildings on this site.
Interface's energy model predicted that the building would use 40 percent less energy than a typical new building and 70 percent less energy than older California community-college facilities. The MUB opened its doors in August 2010 and has since collected a full year's worth of data (see chart, page 63); it missed its original target, but only by 6 percent.
The building houses two specific departments, Child Development & Family Studies and Health Education & Community Health Studies. Each has a main office with an extrawide landing, giving people a place to mingle. However, the 35 classrooms are not limited in use to those two departments. Equipped with the latest technology, they are designed to be a flexible resource for the entire campus and are frequently booked for classes in everything from business accounting to Russian for bilingual students. There are banks of faculty offices, a large computer lab, and group assembly rooms. As students travel up the building, the walkways weave back and forth across the skylit atrium, purposefully designed to encourage chance interactions. "The atrium is part of the sustainability story, but it's also designed intentionally as a social space," says Pfau. To modulate the sound of mingling, acoustic baffles line the walls and ceilings. The baffles are concealed behind wood paneling, which helps warm up a space that might otherwise feel institutional.
On the rooftop, sedum and other hardy plants are making the most of a pretty tough environment. The green roof is not visible to its occupants, but Pfau is hoping the college goes ahead with its plans to put in native landscaping. According to him, the building is just a few points short of LEED Platinum, and some banks of native grasses would do the trick. Preferably, they'll be ones that look good blowing in the wind.