Oak Point's return air runs are hidden next to vertical supports with takeoffs under benches. A combination dehumidifier/boiler saved the city of Plano, TX, money and space.

The new 85,000-sq-ft Oak Point Center recreation complex holds true to the adage that "everything is bigger in Texas." However, because of a new technology and emerging natatorium design concept, the pool equipment room for the complex's 50-meter stretch indoor pool is significantly smaller than its counterparts.

The smaller equipment room saved approximately $38,000 in construction costs. While the savings is a small percentage of the Plano, Texas-based contractor team's cost-cutting hvac system, other design innovation proposals definitely caught the eye of the Plano Parks & Recreation Department. With Oak Point Center now taking a high profile position as one of the top five largest and certainly one of the most state-of-the-art recreation facilities in Texas, the design team's innovations may change the face of future natatorium hvac design.

Much of the credit goes to the project's design consortium consisting of the architect firm, Brinkley Sargent Architects (Dallas); consulting engineering firm, G and S Consulting Engineers LLC (Dallas); and mechanical contractor, H & G Systems, Inc. (Garland, TX). The consortium specified a newly developed swimming pool dehumidifier by Dectron Internationale (Roswell, GA). The equipment choice saved several hundred square feet of valuable space by eliminating conventional and bulky swimming pool water heaters normally located in a natatorium's pool equipment room.

Multifaceted Innovations

Typically a natatorium the size of Oak Point Center uses a dehumidifier(s) to remove moisture and sometimes recover energy to heat the pool water. Meanwhile, large boilers are needed as either primary pool water heaters, back-up heaters, or secondary stage heaters during dump/fill periods.

At Oak Point Center, however, two Dry-O-Tron RS-282 rooftop dehumidifiers each include modular natural gas boilers totaling 1.5 million Btu. While the dehumidifiers keep the space dry (280 lbs/hr of moisture) and recover energy to totally heat the main pool's 624,000 gallons and adjoining leisure pool's 48,000 gallons of water to 82¡F, an onboard glycol-to-water heat exchanger provides supplemental or backup heating (if needed) from a glycol loop connected to the boilers. The boiler/glycol loop combination is also responsible for heating the 30,000-sq-ft indoor pool area to 84¡ via an additional onboard water-to-air heat exchanger.

By opting for the combination dehumidifier/boiler packaged units, the city of Plano saved an additional $15,000 in boiler equipment plus the installation and labor costs associated with running natural gas piping to the pool equipment room.

Another benefit of rooftop boilers is the fact they won't succumb to premature failure from the caustic environment created by chemical gas accumulation found in typical pool equipment rooms. "When subjected to the caustic environment of an equipment room, we've seen situations where gas-fired pool water boilers sometimes fail prematurely after only five years of service," said Mark McMillan, partner, McMillan Choate & Associates, Inc. (Irving, TX), a manufacturer's representative firm that helped put together some of the hvac equipment packages at Oak Point Center.

Besides saving space, the design team also innovated several revolutionary air distribution design ideas. Instead of a single-return air wall diffuser found in typical natatorium designs, Oak Point Center once again strays from convention. Return air is handled with twenty 18-in.-round spiral, corrosion-resistant aluminum ducts (Air Flow Techniques, Albuquerque, NM) along the pool's exterior wall that drop down to 12-in. above the pool deck. To further improve air distribution, each duct has a balancing damper. "We think this is the better way to handle return air and eliminate the possibilities of air stratification," said Paul Joyce, senior mechanical designer, G and S Consulting Engineers, which has designed hvac systems for five other natatoriums.

Supply air distribution is fairly typical with four 24-in.-round ceiling ducts that are positioned equally across the length of the pool. Additional diffusers provide extra dry supply air to the spectators' area and sole wall of windows. Since the Dry-O-Tron introduces approximately 15% (0.5 cfm/sq-ft of deck and pool surface area) outside air to comply with American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) standards, the natatorium is also outfitted with Loren Cook Co., low-profile ceiling exhaust fans to maintain negative air pressure. In the event of air quality emergencies, such as superchlorinating, both the exhaust fans and a special purge feature on the Dry-O-Tron can evacuate the entire facility in a matter of minutes.

Better Indoor Air

While the innovations are important, Amy Fortenberry, recreation superintendent, Plano Parks & Recreation Department, likes the new facility's dry, comfortable indoor air quality compared to Plano's other two indoor pools, Williams Natatorium and Plano Aquatic Center that were built in 1971 and 1978, respectively. Because current dehumidification technology and moisture-fighting construction techniques were not available at the time, both 20,000-sq-ft facilities suffer from poor air quality.

"We really like the fact that spectators, whether they're watching a swimming competition or just waiting for their kids to finish swim class, are staying dry and comfortable," she said.

The rest of the recreation center contains a multitude of facilities including a gymnastics area, classrooms, aerobics center, double gymnasium, four racquetball courts, climbing wall, weight room, running track, and game room. Hvac for these areas is supplied by an array of Trane (La Crosse, WI) rooftop DX constant volume and variable air volume package units. All Oak Point Center hvac is monitored and controlled by a Johnson Controls (Milwaukee) Metasys building automation system. However the natatorium's Metasys-compatible hvac equipment is monitored by the Metasys system, but controlled by Dectron's proprietary microprocessor-based controller, Dotics 9, which can be accessed via onboard or remote keypads and/or telephone modems. ES