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Fabric ducts save metal fabricating plant $500,000

Dec. 15, 2002
In this installment of What Works, a metal fabricating company uses fabric ducts to cut costs.

Saving money is usually a good thing. Saving $500,000 is a very good thing. That's what Star Precision, a metal fabricating company based in Frederick, Colorado, accomplished when it designed its new $6.2 million plant.

Development of the new plant started out predictably enough for the five-year-old company. However, when its consulting engineer delivered a conventional HVAC design that carried a $1-million price tag, convention went out the window. The company formed a new design team consisting of Mark Hayes, vice president of finance, Star Precision; John D'Agostino, mechanical engineer, AC/H Professionals, a Longmont, Colo.-based HVAC contracting firm; and Bradley Bakel, project manager, Construction Concepts, Inc., a Longmont-based general contractor.

Together, team members tracked down a solution that saved Star Precision a half-million dollars and delivered additional, unexpected benefits. "I admit that there were any number of people who questioned my veracity when we started out," says Hayes. "But, those folks have come around. The end result has been better than we could have imagined when we started."

The solution centered using fabric duct, which was lighter, faster to install and less expensive than the traditional round, spiral duct specified by the original consultant. Manufactured by Dubuque, Iowa-based DuctSox, the fabric ductwork eliminated an impediment to forklift mobility, reduced the need for secondary framing to accommodate the heavier roof load anticipated with metal duct, and provided better air dispersion and appearance than metal duct.

Machine tolerances and worker comfort were top considerations for the design team. Star Precision's former 36,000-sq.-ft. plant had little airflow from the eight ductless evaporative coolers, which simply blew conditioned air through the back wall. "Workers were either too cool or too hot because the conditioned air was either drafty or stratified from a poor exhaust design," says Hayes. Equally important was air dispersion around the facility's equipment, which had caused problems at the company's former location when temperature variances produced unpredictable machinery tolerances. "With any type of ductwork, we were concerned with uneven air dispersion around our manufacturing and fabricating equipment because temperature variations can change tolerances and affect quality control," explains Hayes.

The resulting HVAC design keeps the plant at a cool 78°F, even though heat generation by the plant's 30 metal forming and cutting machines (brakes, punch presses, laser cutters, water jet cutters and other machinery) often surpasses 120°F. In fact, since the plant's startup in June, 2002, Hayes says he has only noticed one complaint. "This summer was very hot in Colorado, with 100°F days, and I heard several employees say that the plant was too cold for them. The system works well, with energy costs even a bit lower than our expectations."

A fabric ductwork system helped a metal fabricating plant save $500,000 in construction costs.

 The HVAC system uses eight 23,000-cfm evaporative coolers by Champion Cooler Corp. of Little Rock, Arkansas. The units are paired together with a plenum that runs through the exterior wall and splits into a "Y" shape that supplies each pair of duct runs. Each pair, which spans from 180 ft. to 300 ft., in length, has factory-engineered linear mesh vents installed lengthwise at 6, 7 and 8 o'clock, and at 4, 5, and 6 o'clock.

The main production floor's HVAC design uses strategically placed ceiling and wall fans to eliminate collected hot air at the roof level and exhaust enough air to produce a positive building pressure. Ceiling exhausts are thermostatically controlled to remove heat, while wall fans have sheet metal duct drops 18 in. off the floor to eliminate air stratification and pull air from the 20-ft. high fabric duct. According to Roger Bakel, the original design called for roof-mounted exhaust fans which, when combined with the weight of sheet metal duct system, might have surpassed the ceiling's load-bearing specifications.

"Everybody who looks at what we've done with this HVAC design just can't believe the indoor air quality we've achieved, mainly because they've never heard of fabric duct," says Bakel. "This is really a perfect product for warehouses and industrial plants like this one."

The technology may not be as well known as conventional metal ductwork, but that's likely to change quickly as companies learn of the 20 percent to 80 percent cost savings fabric ductwork generates.

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