The Air in There
Esquimalt Recreation Centre
Esquimalt Township in Victoria, British Columbia
By John Parris Frantz
The architectural combination of metal, glass and wood produces rave reviews at the new Esquimalt Recreation Centre indoor pool, but for the HVAC consulting engineer, Jimmy Ng, these condensation-generating materials presented a dehumidification and air-flow challenge.
Unless the air-flow design had enough throw and consistency, the high humidity loads could have long-term effects on the striking interior design of project architect Cannon Design in Victoria, British Columbia. Condensation possibly could cloud the hundreds of square feet of window surfaces while deteriorating the metal and wood structure in the long run.
Besides the material concern, Ng, a project engineer at Stantec Consulting Ltd. in Vancouver, also faced a myriad of moisture-generating pools at different temperatures including a 78-foot-by-42-foot lane pool at 85ºF, a 16-foot-by-16-foot children's pool at 90ºF, a 14-foot-diameter spa at 105ºF and a 40-foot-by-60-foot leisure pool at 90ºF. The natatorium, which is part of an $8.1 million renovation and addition to the existing 30-year-old recreation building, also includes moisture-generating toys such as fountains and water canons that add to the large humidity load.
Combining those moisture-elimination challenges with Recreation Centre Operations Manager Yves Bienvenu's request for value engineering, Ng realized the 12,000-square-foot natatorium's HVAC design would test his design team's expertise. While the majority of the center's other HVAC engineering duties were handled by another firm, Stantec was chosen for the natatorium portion of the project because of its prior indoor pool work.
"This was probably the most difficult indoor pool project we've ever designed," Ng says.
Part of Stantec's value engineering included eliminating under-deck ductwork, which commonly is used to keep the bottom of windows and walls free of condensation. Instead, his strategy of maintaining a 55 percent relative humidity throughout the space relied on Victoria's moderate climate and using only overhead ductwork, which saved 15 percent in total HVAC costs.
"Under-deck ductwork is certainly nice to have and mandatory in a cold climate, but I didn't think we needed it if our overhead system was designed correctly," Ng says.
Saving another 20 percent in ductwork materials and installation labor was the specification of white fabric duct from DuctSox instead of traditional spiral metal duct. DuctSox's Sedona model was less expensive than metal duct, which needs protective epoxy paint coatings in the corrosive environment of humidity and pool chemicals.
Aesthetically, the clean lines of the fabric duct replace the ribbed look of metal and add to the futuristic architecture of the facility.
Although he knew it would save money, Ng was concerned with the air-delivery performance of fabric due to his lack of exposure to the product. However, Gerry Lentz, a sales engineer, worked with Ng to have DuctSox factory-engineer each duct section with the necessary Sonic Vent perforation sizes and placement to assure proper air throw and consistency.
To control proper space temperature near all four bodies of water, Ng divided the room's air distribution into four zones. The room's perimeter system, which is designed to bathe the walls in 85ºF, 55 percent relative-humidity air, uses linear Sonic Vents at the 6 o'clock and 4 o'clock positions. The other three zones are over the smaller pools. The fabric duct is hung from a corrosion-proof aluminum H-track hanging system.
"With the problems of metal in a corrosive environment along with the costs involved with applying and maintaining the necessary protective epoxy coatings, fabric duct seems to be a perfect air distribution system for indoor pools," Ng says.
Because of a learning curve for first-time fabric duct installation, the fabric duct was installed in about the same time as metal duct. However, Rick Carter, a 25-year-veteran project manager, says any future project would probably result in a considerable labor difference between fabric and metal because of the gained experience.
"I was worried about the unknowns when we started installing fabric, but after it was finished I was quite impressed with its structural integrity and the look," he says.
Balancing the fabric duct took only a half-hour because airflow and static pressures were factory-engineered into the fabric-duct diameter and each linear vent along the length of each duct run.
The space's indoor air quality is maintained by a Dectron Dry-O-Tron heat-recovery dehumidifier that removes 400 pounds of moisture/hour while also providing cooling or heating for the space. It uses heat recovery to provide free pool water heating for the room's largest pool. The other three vessels' individual temperature demands are met with separate boilers and Armstrong Pumps Inc. heat exchangers to keep strict temperature control that's monitored and controlled by a Honeywell direct digital control system.
While cost cutting and corrosion control was the impetus for fabric duct in the natatorium, the 5,000-square-foot gym's mission was maintenance. Metal duct in open architecture gym settings is susceptible to dents from errant objects. Fabric duct takes hits and simply regains its form. Along with air flow evenness and aesthetics, maintenance was a major reason Paul Timmins, principal at the consulting engineering firm for the gym, Hirschfield Williams Timmins Ltd., specified fabric duct. Ventilation is supplied by a 6,000-cfm gas-fired outside air ventilator by Engineered Air in Calgary, Alberta.
The success of the project is already evident in that Stantec recently presented the project at an American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) meeting with rave reviews.
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