July 1, 2009
Officials with Millcreek Engineering Co., working on a new community center in Washington City, Utah, wanted to save money while ensuring good airflow.
The $17 million, 110,000-square-foot structure was to include a senior center and disaster relief facility along with two pools, three gyms and several fitness rooms.
Millcreek was faced with a choice for distributing air through such a large building: conventional metal ductwork or fabric duct. Company principal Rick Hoggan, a licensed professional engineer, was pretty sure fabric duct would work, but he needed to use some modeling software to prove it.
Using the company’s own proprietary program, he performed a value-engineered redesign of the HVAC system comparing the performance of the two systems. It proved the fabric duct’s linear diffusion would provide more even air distribution in the community center.
A bigger bonus: It would save 30 percent on materials and labor and make installation 25 percent faster, according to the software.
The choice“There was some resistance in the beginning because of the unfamiliarity with fabric duct,” Hoggan said. “But everyone agrees now it was the right choice.”
In the case of the Utah center, the fabric duct chosen was Verona, made by Dubuque, Iowa-based DuctSox Corp. Its Comfort-Flow design permits 15 percent of the air to move through the fabric itself - eliminating condensation, corrosion and rust, according to DuctSox officials.
That was especially important with the community center, since it features 40,000 square feet of pool space, with its high humidity and chlorine-heavy air.
Millcreek officials said the computer modeling was especially helpful in conditioning the pool area’s bleachers. It has a separate, 5,000 cfm perimeter-airflow system. At 75°F, it is kept five degrees cooler than the pool below.
An unusual feature of the center’s pool complex is the large, retractable wall of windows, which is often opened during the summer. The HVAC system is designed to move warm, dry air over the windows during the winter to prevent condensation.
Winter temperatures in Washington City, Utah, are often below freezing.
The design has the added benefit of keeping swimmers more comfortable and lowering the pool water’s evaporation rate.
As they were designing the center, Millcreek discovered that using fabric duct reduced the number of high-volume, low-speed fans needed to hang from the center’s 45-foot-high ceilings.
A Carrier Corp. 200-ton AquaForce chiller with several load settings and two 179,000-Btuh boilers from Weil-McLain make up the chilled-water, hot-water loop. Carrier air handlers, along with Venmar stainless steel air handlers, sit on the roof above the pool.
With the equipment, the complex saves 25 percent on its annual energy costs, Hoggan said.
The problem of fabric duct’s “flat” appearance during times when air is not moving through it has been fixed with DuctSox’s suspension system, which connects to the ductwork in three places and makes it appear inflated.
Hoggan worked with Jeff Thomson at manufacturer representative Mechanical Products Intermountain, and two St. George, Utah, companies - Sunshine Heating & Air Conditioning, and Watts Construction - on the project.
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