The Oskaloosa, Iowa-based institution’s latest project features geothermal heating-cooling, fabric ductwork, energy recovery ventilators (ERVs), building automation system and other technology, making them two of the greenest campus buildings in the Midwest.
Fabric ductwork by DuctSox, an underground geothermal field system anchored with water-source heat pumps by Trane, and Semco ERVs is what makes the 155,000-square-foot Penn Activity Center (PAC) the most efficient building on campus, according to Michael Vogt, a project engineer for design-build mechanical contractor, Cunningham Inc.
Cunningham’s green design helped the university qualify for a $275,000 incentive by local utility MidAmerican Energy. Additionally, the Associated Building Contractors (ABC) of Iowa recently recognized the design with a first place award in its Excellence in HVAC competition.
Vogt said the sustainable combination of geothermal, fabric duct, and ERVs would typically earn points for Leadership in Energy and Environmental Design (LEED®) certification by the U.S. Green Building Council. While fabric duct’s main purpose was to save the value-engineered project over 60 percent in HVAC ductwork installation costs, it also offers a green strategy of evenly distributed heating-cooling space temperatures. This leads to shorter, energy-saving mechanical equipment run times, said officials at DuctSox.
Fabric duct also helped Cunningham solve engineering problems presented by the PAC’s aesthetic gable roof that rises to a 45-foot-high pinnacle. While high ceilings are mandatory for sports activity height clearances, they also necessitate an air distribution system with a high throw capable of reaching the floor. The four 290-foot runs of 48-inch-round TufTex that Vogt specified has 3-inch diameter high throw orifices running the entire length, capable of reaching the floor with heat in the winter.
“There’s a noticeable difference between the air comfort in the PAC and other large athletic buildings,” said Vogt. “Plus, the college saved tens of thousands of dollars in installation labor costs because lightweight fabric duct is so fast and safe for workers to install in elevated places.”
Maintaining air comfort on the second floor perimeter running track was an air distribution challenge as well. While the 200-foot-long ducts condition the track on each long side, the building’s shorter end caps are independently supplied each with a 100-foot-long run. One end supplies the third floor mezzanine cardiovascular workout area and has factory-engineered orifices that allow the air to evenly spill down to the track on the second floor.
The main disadvantage to fabric duct in the past was its limp appearance when not inflated during idle equipment periods. However, Cunningham’s specification of 3 by 1 hanging system, which supports the duct at the 10, 12 and 2 o’clock positions, makes the duct look 85 percent inflated during idle periods.
Perhaps the major energy saver on the project is the geothermal system that supplies the ductwork for the PAC and the 55,000-square-foot academic building, the Musco Technology Center (MTC). The PAC’s six 20-ton heat pumps continually receive 55°F water from a geothermal well field that both buildings draw from with two 460-V, 25 hp. pumps. The well field has 25 miles of underground horizontal piping bored at 15-, 30- and 45-foot depths by contractor A-One Geothermal, Earlham, Iowa. Varieties of smaller heat pumps are located throughout the facility servicing locker rooms, showers, offices, and exercise rooms.
While the geothermal system handles the sensible heat load of the building, Vogt specified various ERVs to handle the latent heat load by recovering energy from the return air.
Cunningham’s design also featured energy-saving flexibility wherein everyday routine activities are handled with minimum energy usage. However, during larger capacities of up to 3,000 people such as graduation or other special events, the CO2 sensors activate the HVAC systems to full capability.
The MTC is named after Musco Sports Lighting whose president and CEO, Joe Crookham, donated $12 million to the project.