Fabric HVAC Retrofit Improves Workplace
Staff -- Consulting-Specifying Engineer, 3/1/2001
Until recently, many manufacturing plants considered indoor-air quality (IAQ) an unnecessary expense. But with today's labor shortages and escalating turnover of increasingly selective employees who seek better working conditions, manufacturers are looking to IAQ improvement as a method of keeping employees and attracting new ones.
A printing plant in Winchester, Virginia, illustrates the severity of this predicament. The 200,000-square-foot plant was operating 24/7, but couldn't continually field a full factory staff partially due to uncomfortable working conditions. Regular summer indoor temperatures of 105°F due to open-flame bookbinding machines, combined with typical heat loads of industrial machinery, made working conditions nearly unbearable. Additionally, high dust-particle counts and a negative building pressure added to the IAQ woes.
The owners of the printing plant agreed that something needed to be done to change their working conditions. The only question was how to accomplish this in an efficient-and also cost-effective-way. With original bids far out of their price range, the project was initially shelved as the owners weren't entirely sure that it could be done. But then a new proposal offered a different approach.
A fabric idea
The new design team proposed that two 275-ton, rotary-screw compressor chillers supply glycol to four 40,000-cfm air handlers with six-pass coils. The four air-handling units would dehumidify and cool the supply air, and connect to 64-inch-diameter round fabric ducts that reduce down to 8- to 24-inch-diameter lateral supply ducts.
Instead of cooling the entire plant, the designers decided that a more efficient method would be to spot-cool roughly 60 workstations. The fabric duct, which comes in custom-engineered grades of permeability, supplies a draftless airflow that drifts into each workstation.
The design was a cost-efficient use of refrigeration equipment, but the fabric duct reaped the largest savings. The 5,000 linear feet of 100-percent polyester air distribution saved an estimated $800,000 over traditional metal-duct, labor, material and installation costs.
Because the installation time for the fabric duct was reduced to just five weeks-as opposed to an estimated six months for metal duct-the factory lost no production time. Additionally, the low weight of the fabric air-distribution system-90 percent less than metal-saved the plant from possible structural issues and additional roof supports.
Overall, it was agreed that the fabric ductwork not only made for a successful project, but was also the main reason the project went forward in the first place.
"I had never heard of fabric duct until this project and I thought [the engineer] was joking when he first suggested it," recalls J.J. Crewe, the contractor on the project. "Fabric duct is pretty new in the United States, but in Europe it's very common. This project never would have materialized without using fabric duct because the client just couldn't afford the more expensive alternatives."
For more information on custom-made fabric ductwork by FabricAir, Inc., circle 102 on the Reader Service Card on page 65.
