Fabric Duct Meets Unique Challenges of University of Chicago Lab Building
With most buildings, air distribution is a straightforward mechanical-engineering task. With The University of Chicago's new $200 million, 427,000-sq-ft Ellen and Melvin Gordon Center for Integrative Science—particularly three small laboratories in which state-of-the-art laser-based physics research was to be performed—it was anything but.
“The research professor didn't want to feel or hear the airflow from the labs' ductwork because it might affect the laser experiments,” laboratory manager John Phillips said.
As Peter Pogorski, a principal of Cambridge, Mass.-based architectural firm Ellenzweig, explained: “HVAC air-system turbulence or a lack of temperature uniformity from disproportionate airflows in these types of physics labs can cause very sophisticated and expensive instruments, such as lasers and electron microscopes, to go out of alignment at nanoscale, degrading their precision. The instrumentation can get very hot quickly; it is vulnerable to internal condensation, structural or airborne vibration, and contamination, such as dust, so providing a stable lab environment requires sophisticated products, engineering, and installation.”
Providing a discharge-airflow velocity of less than 25 fpm while maintaining a 70°F (±1°F) temperature is nearly impossible with conventional HVAC metal duct/register systems. Thus, Steve Levin, a principal of Watertown, Mass.-based Bard, Rao + Athanas Consulting Engineers LLC (BR+A), specified cylindrical LabSox fabric duct from DuctSox Corp. for the three laser-based-physics-research laboratories.
“Just sound waves from a person's voice or a gentle draft from an HVAC duct can skew electron-microsopy scans,” Phillips said, “so airflow must be very subtle, with no noise or turbulence.”
LabSox low-throw fabric ducts disperse air gently and evenly at feet-per-minute rates lower than those with typical metal duct/register systems.
Mechanical contractor F.E. Moran Inc. of Northbrook, Ill., completed the building's HVAC work, while Kirby Sheet Metal Works Inc. of Chicago served as build-to-suit contractor after a newly hired researcher requested more stringent HVAC performance in three generically designed labs. The fabric duct eased installation, which, given the predominance of existing utility piping, would have been difficult with conventional metal duct, Robert Simek, project manager, Kirby Sheet Metal Works, said.
Each laboratory has two 12-ft-long runs with diameters of 9 to 12 in. suspended by H-Track systems, which minimize sway. Air Products Equipment Co. of Elk Grove Village, Ill., assisted with sizing, permeability, and other factory-engineered features of the fabric duct.
To supply the building, BR+A specified a Filtrine Manufacturing Co. chiller that provides chilled water to nine 100-percent-outside-air packaged units with variable-frequency drives (VFDs) from Enviro-Tec by Johnson Controls located in the basement. To supply the three laser-based-physics-research laboratories, the building's central system provides outside air to three 1,000- to 1,500-cfm dehumidifying units to maintain relative humidity under 40 percent. Like all of the laboratories, the physics labs with fabric ductwork use VFDs for proper air balancing.
Johnson Controls provided the building-management system, which monitors and controls each laboratory's supply and exhaust system with a slight positive pressure.
When it needs cleaning, fabric duct can be disassembled easily and laundered.
“It seems many physicists would be happy with a Space Shuttle on earth where there's zero gravity and zero atmosphere,” Pogorski said, “but until that happens, it looks like fabric duct is excellent for laboratories that require minimum turbulence and noise combined with even air dispersion.”