Fabric Ducts Help Meet High-Tech Data Storage Facility’s Needs
That was the hand dealt to consulting engineer Scott Henriques, P.E., project manager, and Nora McCawley, senior hvac designer, both of Shooshanian Engineering, Boston, MA; and mechanical contractor Victory Heating & Air Conditioning, Bellingham, MA, for data storage manufacturer EMC Corp., Hopkinton, MA.
Typically, an engineer might specify ceiling-hung metal duct for the 50,000-sq-ft building (in Milford, MA) that EMC was converting into a media solutions/software development lab with accompanying offices. However, the estimated tens of thousands of dollars in structural support needed for the 18-ft-high metal deck roof would have ballooned the budget.
An additional challenge was the mandatory low-decibel airflow stipulated by Mark Flanagan and Mark Urbanek, EMS’s project manager and director of construction services, respectively. The techniques involved with the particular software development and application work performed in the lab mandated the quietest conditions possible.
LIGHTWEIGHT AND COOLShooshanian’s design solved the load-bearing and noise-attenuation problems by specifying a fabric duct air distribution system (manufactured by FabricAir®, Louisville, KY). Fabric ductwork is 90% lighter than metal duct, and requires considerably less installation labor, the manufacturer says.
This fabric duct is factory engineered for airflow permeability through the polyester-based material, the manufacturer says, claiming that it is the quietest ductwork type in the hvac industry. It has been used in recording studios, theaters, and other sound-sensitive applications.
Henriques had still one more challenge. He was asked to adapt 16 used Trane and Carrier air handlers, totaling some 180,000 cfm, from another EMC property, for use here in Milford. EMC either had to use this existing equipment, or wait 20 to 30 weeks for computer room precision air conditioning equipment, which was back ordered due to the earlier dot.com building craze.
The waiting period was deemed unacceptable. “The air handlers aren’t redundant equipment, but we figured in some over capacity to allow for equipment failure or routine maintenance shutdowns,” Henriques said.
He was able to specify some new equipment, however: three new air-cooled, 130-ton Carrier chillers, which supply the air handlers.
WORK FASTAnother critical challenge was the project’s fast-track timetable. EMC needed occupancy ASAP to accommodate its growth in the high-tech industry.
“Because we weren’t afforded the time to do a complete and detailed design, I can remember sometimes going to the site and literally drawing plans on a piece of paper so the contractor could continue working, then going back to the office and putting it on CAD,” recalled Henriques.
The design calls for the 15,000-sq-ft lab to be surrounded on three sides by a mechanical room, with a hallway between the spaces housing the floor-mounted air handlers. Part of the air conditioning supplies an electronic equipment area using a raised-floor plenum design.
The air distribution inside the lab was more complicated, requiring gradual, draft-free airflow increases. These were accomplished with different grades of fabric permeability that FabricAir custom designed. The six 100-ft-long duct runs begin with a specification of 32 cfm per linear ft and end with 250 cfm per linear ft. The lab’s 30-in.-dia duct system consists of 4,300 sq ft of fabric, giving an average air diffusion velocity of 16 fpm.
“Because of the way the return air was set up, we wanted to dump more air out into the far reaches of the space, to provide for good air movement,” said Henriques, who also specified the duct color to match EMC’s corporate blue.
For Victory Heating & Air, everything had to be mounted to the floor, including return lines, plenums, and metal supply ductwork that supplies the fabric duct.
In the end, EMC saved thousands of dollars by eliminating the need for additional ceiling structural work to support the air-handling system. The fabric also brought down project costs by reducing installation labor costs.
Publication date: 02/18/2002