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Originally, the president of Kerr-Greulich Engineers Inc. in Louisville, plus design team co-members, Edward West P.E., director of WKY construction management services, and Tony Kleyer, vice president of project architecture firm Louis & Henry, considered ceiling-hung metal ductwork that would distribute air to the arena's 10,000 capacity spectators as well as the basketball floor. The 42-year-old structure had a previous design that was a heat-only system from mezzanine level air handlers.
When structural consultants proved the dome-shaped roof was already near load bearing capacity, Greulich was forced to look at alternatives such as lightweight fabric duct instead of traditional ceiling-hung metal ductwork. The fabric duct proved to be 90 percent lighter than similar sized metal ducts thus allowing the preferred ceiling distribution. It also saved the project $75,000 in materials while providing a more even air dispersion than metal duct registers.
"Fabric duct provided a good solution to the structural hurdles we faced with the Diddle renovation," said West. "Plus it also provided some aesthetic value from something you would normally want hidden - ductwork."
Greulich specified TufTexâ„¢ fabric duct by DuctSox. Installed by Haase Heating & Air Conditioning and overseen by mechanical contractor Hussung Mechanical Contractors Inc., the 720 linear feet of round 36 inch diameter duct is positioned 30 feet above the spectator section and 70 feet from the basketball floor.
While the previous system was considered noisy, the design team reduced HVAC operational noise substantially. Even though fabric transmits less HVAC mechanical noise than metal duct, Greulich also specified duct attenuators by Commercial Acoustics and 12,000 cfm Trane air handlers with built-in sound attenuation characteristics.
The custom-colored "Hilltopper" red duct hangs like a banner when not supplied with air. Large diameter fabric duct from 38 inches to 80 inches in diameter requires a dual raise system for aesthetics and weight-bearing purposes. Greulich and Kleyer specified the largest diameter DuctSox possible for single rail hanging and then built the supply air portion of the HVAC systems around the duct size.
"Using the fabric duct system as a continuous WKU red-colored â€˜banner' inside this circular building gave the design team yet another opportunity to provide visual excitement for the renovated building's interior environment. The red banner really has added an additional layer of aesthetic richness for the Diddle Arena renovation. It has helped to bring a 20th century building into our current century," said Kleyer.
The rail system was hung with Gripple Inc. hangers attached to the domed ceiling. Since the ductwork is easily disassembled, the university is considering silk-screening its logo or paid advertising on the duct when it's taken down for future laundering.
The air handlers are supplied with two new 400-ton Trane chillers. Heating is handled with each air handler's on-board 4-million Btu boiler. Although the university has a district steam plant, Greulich specified on-board boilers for better control since the district system doesn't provide heat year-round.
The building is controlled to a temperature range of 68 degrees to 75 degrees F with a Johnson Controls Metasys building control system. If either temperature is surpassed, heat or cooling is activated. Greulich designed the space for continuous ventilation, but it is controlled by proportionate control valves that mix makeup air with recirculated air in the air handlers. Outside air is introduced as needed and is determined by carbon dioxide sensors that open or close outdoor dampers on each air handler.
Additional time and money was saved with fabric duct when the air distribution design needed a rerouting soon after installation to allow site lines to two large screen monitors and luxury skyboxes that were late add-ons to the arena's design. Rerouting metal ductwork would have delayed the project an extra week or two versus the modification of fabric duct. Instead, DuctSox factory-engineered lateral and vertical changes that included eight 45-degree elbows and 18 tees - complete with factory-installed internal flow straightening devices - based on Hussung's field measurements. The additional ductwork was completed with an estimated cost savings to the university of $10,000 vs. metal duct, according to Greulich.
Publication date: 11/24/2003