Consulting engineering firm Progressive Design Collaborative teamed up with architecture firm Smith Sinnett Architecture to make the transformation happen. With the encouragement of RCC’s Cindi Goodwin, director of facilities at the Asheboro, NC-based technical school, the team says it designed one of the nation’s first combination of active chilled beams with an off-peak hours ice storage/chilled water loop.
The foundation of the continuing education center’s cooling system is 184 IQHC active chilled beams and two Pinnacle® dedicated outdoor air systems — both products manufactured by SEMCO. The chilled water loop is supplied by a 130-ton Model CGAM air-cooled chiller with scroll technology manufactured by Trane, and an ice storage system by Calmac. All mechanical systems were installed by American Industrial of Greensboro, NC.
The two-pipe chilled beams, which range from 2 ft to 10 ft in length, supply 100% of the $7.6-million facility’s cooling. Chilled beams have the potential for condensation in humid environments such as North Carolina. Therefore PDC’s DOAS specification delivers dry outdoor air to the chilled beams to prevent condensation and comply with ASHRAE Standard 62.
Besides providing a comfortable relative humidity, the DOAS/chilled beam cooling strategy’s comparatively small 6-in-diameter ductwork saves significant ceiling space. Chilled beams also use approximately 40% less fan horsepower versus the alternative of a conventional rooftop and ductwork system.
“We wanted to keep ceiling heights at 10 ft, so the inherent feature of the active chilled beams’ reduced duct sizes caught our interest,” said Scott Ennis, project engineer.
Ennis had never specified a chilled beam project before, but is already specifying them again for a hospital with low ceilings.
Besides indoor air comfort, the two 10,000-cfm DOAS systems also add to the project’s sustainability and IAQ because they use molecular-sieve enthalpy wheel technology to dehumidify outdoor air and recover heat from exhaust air for pre-heating outdoor air. Versus silica gel desiccant wheels, the DOAS’ molecular-sieve technology quickly adsorbs the exhaust air’s moisture, but not its contaminants that can potentially pollute incoming outdoor air and degenerate IAQ. The enthalpy wheel also uses acid-resistant, anti-microbial and anti-stick coating treatments that help sustain the equipment’s lifecycle and helps maintain design static pressures.
The CEIC’s energy savings result in a six-year payback of the mechanical, electrical, and plumbing specification. The greatest savings were realized with the chilled beams and energy recovery DOAS; ice storage; VF on the piping loops and DOAS fans; high-output T-8 fluorescent lighting; VAV boxes with their own dedicated hot water loop; a solar domestic hot water heating system by Lochinvar; a 3,200-gallon rainwater harvesting tank; various MEP equipment; and polypropylene manufactured by Aquatherm. The polypropylene was used on piping runs less than 3-in in diameter. The pipe is less expensive to produce, install and run, and helped attribute to LEED credits;
The payback is reduced to four years when considering the $60,000 utility rebate. Duke Energy/Progress Energy offered the incentive because the CEIC’s chiller operates mostly at night and is needed rarely, if at all, during daytime high-peak electric rate periods.
The LEED 2.2 project’s HVAC equipment is also racking up approximately seven credits of the total 41-credits submitted for LEED Gold certification.
The CEIC, also uses a separate hot water loop and VAV box hot water coils that are supplied by two Lochinvar condensing boilers and VFD-controlled pumps by Bell & Gossett. Specifying a separate heating loop saved tens of thousands of dollars in installation labor and material costs versus piping hot water to each chilled beam.
Based on the project’s energy efficiency, many of the CEIC’s HVAC technologies will be combined in future PDC projects, especially schools and hospitals, according to Ennis.
Converting an old warehouse into a sustainable showcase was a challenging project. Therefore, RCC proudly promotes the project’s energy savings with its BuildingLogiX building automation system’s EcoRate dashboard. The wall-mounted dashboard in the CEIC’s lobby allows any visitor touch-screen access to a real-time analysis of the facility’s ongoing water and energy savings.