Going for a Spin: Enthalpy wheels flood the Ohlone College Newark Center for Health Sciences and Technology with fresh air.
When the San Francisco office of Perkins+Will originally master-planned a second Newark, California–based campus for Ohlone College, the design team assumed it would ostensibly replicate the broad program of its original strip-mall location in nearby Fremont. Six months into the process, however, a new college head put a halt to the copycatting.
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Firm principal Howard Weiss recalls of the new president, Douglas Treadway, “He decided all the health-science and technology programs should migrate to this campus. He also felt very strongly that the issue of sustainability is very important—not just from a overall societal perspective, but also in terms of reducing the cost of energy in preparation for budget cuts.” To signal the importance of sustainability, the new building, Treadway proclaimed, would boast an entirely new environmental studies program.
Located on an 81-acre brownfield site adjacent to San Francisco Bay, the Ohlone College Newark Center for Health Sciences and Technology opened in January 2008.
To determine which active sustainability technologies would be employed in the building, MEP consultant Alfa Tech undertook a series of energy studies considering the pros and cons of a half-dozen different options according to performance and cost. “We built a computer model in EnergyPro,” says Alfa Tech partner Michael Lucas. “You can try different systems, as well as different components within those systems.” The team came up with a “strange cocktail” comprising horizontal-bore geothermal heating and cooling featuring 26 miles of pipe, 35,000 square feet of photovoltaics funded partly by the California Solar Initiative, and two 16-foot-diameter enthalpy wheels.
Not commonly used in California, enthalpy wheels are rotary air-to-air heat exchangers. To mitigate respiratory distress, which can affect student retention rates, Treadway and his colleagues at the college wanted operable windows to be part of the design, despite the fact that open windows can overburden an air-conditioning system. So, in lieu of operable windows, Perkins+Will, Alfa Tech, and the client ultimately compromised by sealing the windows and instead installing enthalpy wheels, which flush the class and lab spaces with fresh air without greatly sacrificing the interior climate to the outdoors.
Thanks to their hygroscopic (moisture-retaining) material, the wheels recover warmth as well as humidity from the exhaust air systems. The wheels are housed within 20-feet-square steel boxes and handle 52,000 cubic feet of air per minute, tripling the amount of fresh air required by California Title 24. “It feels as if all the windows are open,” Lucas says, even though they are closed. He also clarifies that the system installation includes filters that clean the outdoor air twice before entering the school interior.
Energy use is 15.39 Kbtu per square foot per year, or $0.48 per square foot per year. “When we modeled this building, our prediction for energy consumption wasn’t anything like the actual. It was significantly more,” Lucas says. “We think the enthalpy wheels are taking care of most of the air-conditioning and heating; you rarely hear the compressors kick on.” The Ohlone team is working with EnergyPro to reprogram its modeling software to better account for its components.
Perkins+Will has also educated Ohlone students about the enthalpy wheels. For example, a six-foot-diameter circular portal allows occupants to observe the relatively silent system and a real-time performance readout. “We used the architecture to support the alternative-energy systems part of the environmental studies curriculum,” says Perkins+Will project architect Susan Seastone, LEED AP. The wheels are expressed on the building exterior, too, placed near the center of the plan (which minimizes ductwork) and distinguished by louvers. It’s a proud point of difference from other projects, which typically relegate enthalpy wheels to basements, Seastone says.
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