Thinking Outside the Box

Scott Ennis, project engineer at PDC, and Steve Campbell, president of PDC, thought well beyond convention with the encouragement of Cindi Goodwin, director of facilities at RCC. They designed one of the nation’s first combinations of active chilled beams with an off-peak-hours ice storage/chilled-water loop.

The foundation of RCC’s Continuing Education and Industrial Center’s (CEIC) cooling system consists of 184 IQHC active chilled beams and two Pinnacle® dedicated outdoor air systems (DOAS), both manufactured by Semco LLC. 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 Contractors Inc., Greensboro, N.C.

The two-pipe chilled beams, which range from 2-10 feet in length, supply 100 percent of the $7.6 million facility’s cooling needs. Chilled beams have the potential for condensation in humid environments such as North Carolina, so 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 (rh), the DOAS/chilled beam cooling system’s comparatively small 6-inch diameter duct-work saves significant ceiling space. Chilled beams have shown to use as much as 40 percent less fan horsepower than conventional rooftop and ductwork systems.

“We wanted to keep ceiling heights at 10 feet, so the inherent feature of the active chilled beams’ reduced duct sizes caught our interest,” said Ennis, who had never specified a chilled beam project before RCC, but who is already specifying another chilled beam project 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 preheating outdoor air. 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 maintain design static pressures.

Building Envelope Design

The building envelope was a LEED challenge for Robert Carmac, an architect with Smith Sinnett Architecture, Raleigh, N.C., because it lacked a vapor barrier, insulation, and other modern energy-efficient building materials. The original building’s wall and roof insulating values were low at R-3.45 and R-7.17, respectively. However, spray foam insulation was able to increase the wall and roof R values to R-14 and R-30, respectively, which are considerably higher than the minimum building code requirement of R-5.7 and R-15.

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 and Campbell.

Huge Savings, Short Payback

The CEIC’s comprehensive energy savings result in a six-year payback of the mechanical, electrical, and plumbing (MEP) specifications with the following equipment generating the greatest savings:

• Chilled beams and energy recovery DOAS;

• Ice storage;

• Variable-frequency drives (VFD) on the piping loops and DOAS fans;

• High-output T-8 fluorescent lighting by Philips Lighting with Wattstopper occupancy sensors;

• Variable-air volume (VAV) boxes with their own dedicated hot water loop;

• Solar domestic hot water heating system by Lochinvar LLC;

• A 3,200-gallon rainwater harvesting tank;

• Polypropylene manufactured by Aquatherm, which was used on piping runs less than 3 inches in diameter; and

• Various other MEP equipment.

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, according to David McDaniel, Brady Trane sales engineer, Morrisville, N.C. When compared to a more conventional design, such as ASHRAE-dictated constant-volume package-rooftop HVAC units with VAV boxes, the college is saving 28.2 percent with PDC’s innovative mix of high-efficiency technologies. The LEED 2.2 project’s HVAC equipment is accountable for roughly seven of the 41 credits submitted for LEED Gold certification.

The CEIC, which is also recognized as the first North Carolina community college project to become a challenge partner of the U.S. Department of Energy’s (DOE) Better Building Challenge program, 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, a Xylem brand. 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.

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.

Publication date: 8/5/2013 

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