A breath of fresh air
Now the school's medical center, following a multiyear expansion project, will also have the most up-to-date HVAC technology. The $95 million, 9-story Medical Research Building, commonly called MRB III, incorporates 340,000 square feet of laboratories for bioscience teaching and medical research. The mechanical systems include ultra-high-efficiency vane-axial supply and exhaust systems, air-to-air heat recovery, and variable-air volume fume-hood-tracking controls. The acoustically engineered, custom VAV air-handling units deliver 450,000-460,000 cfm (cubic feet per minute) of preconditioned, 100-percent outdoor air to the laboratories.
Key to the mechanical system's design was an enclosure that provides structural support and acoustic treatment for the vertically arranged air-handling equipment, including fans and blowers, preheaters, and dehumidification coils. The acoustic panels used to fabricate the enclosure were manufactured by Columbia, Mo.-based Semco Inc.
They were critical to the structural integrity of the compact, vertical air-handling design, according to Bill Baldwin, HVAC division field coordinator at Nashville Machine Co., the building's mechanical contractor.
Many challengesMRB III's layout posed many challenges for the Phoenix Design Group Inc. of Nashville, an architectural-design consulting firm that specializes in medical-construction projects. The building Boston's William Wilson Associated Architects Inc. designed called for an extremely high air-handling capacity for the research labs, but allowed limited space in the penthouse for the air-delivery equipment.
"The air-handling system just wouldn't fit in the available footprint of the penthouse," said Tom Fisher, Phoenix Design vice president. "It was physically impossible to arrange 450,000 cfm of air delivery equipment in the penthouse, so we switched to custom vertical, 2-story units that draw in air through a four-sided coil."
The Compac Space Fan System, manufactured by M&I Air Systems Engineering of Mississauga, Ontario, featured vane-axial fans that use up to 60 percent less space in mechanical rooms and provide efficient volume control through their variable pitch-in-motion feature, according to company officials.
In the laboratories, variable-volume exhaust headers collect air on each floor. Forty-two 30-inch exhaust risers were placed against double-wall Semco plenums at the penthouse level, which direct the air horizontally through air-to-air heat-recovery exchangers. The exhaust air is then drawn up into vertical, variable-speed, vane-axial exhaust fans and discharged through stacks. The exhaust and makeup-air plenums were constructed with Semco panels to channel the air through the filters and heat-recovery exchanger. Outdoor air enters in the upper-level mezzanine and passes through the air-to-air heat exchangers to preheat or cool the outdoor air with recovered energy from the exhaust air.
Multilevel plenums usedAs Fisher explains, "No one could envision the actual air path through the multilevel plenum chambers; it's pretty tortuous. Bill Baldwin at Nashville Machine constructed a 3-D model to help everyone understand the plenum chambers and the route of the air. But the air-handling system is one of the best operating systems that we've done. It's unbelievably well-balanced and stable."
However, it still wasn't an easy project, he added. Supporting the air-handling equipment was a challenge.
"All of these stacked plenums had to be structurally independent of the building," Fisher said. "We couldn't count on the structural steel from the building. It was like a barn with two-story compartments. We needed to have a proven system with structural integrity, with the frame built into it."
Fisher added the materials used in the panels were critical to the design.
"Much of the exhaust air originates from chemical fume hoods, not just room exhaust," Fisher explained. "We wanted the entire plenum system to be stainless steel along the exhaust path, from the point of connection to the vertical risers to the discharge of the stacks. The panels also had to withstand up to 10 inches (water column) of negative internal pressure."
Lots of panelsSemco's panels were chosen. Almost 60,000 square feet of acoustical/thermal panels, removable panels, and access doors were delivered to accommodate the field-built air-handling units, according to Semco senior regional sales manager John Gramke.
Nashville Machine's Bill Baldwin recalled that the panels filled up 30 flatbed trucks and covered the 20,000-square-foot penthouse.
The 4-inch-thick, double-wall panels, which feature roll-formed tongue and groove joints, were supplied in six different material combinations including exteriors ranging from 16- and 18-gauge solid 316-2B stainless and galvanized steel to 18- and 22-gauge solid and perforated 316-2B stainless and galvanized steel and a design pressure of 10 inches water column positive/negative. The access doors and removable panels, which included 12-by-12-inch double-pane wire-glass view windows, ball-bearing hinges, and wedge-lever latches, were shipped pre-hung in wrap-around frames with full perimeter gaskets and factory-installed hardware.
This complex project might not have been successful without teamwork among Phoenix Design, Nashville Machine, Semco and other partners, officials said.
"To say that this project encountered problems and challenges along the way is an understatement equal to that of a politician," Baldwin joked. "The project design was unique, in that it had not been done before that I know of, and its sheer size was unequal to anything in my experience."
Team effortsGramke, Semco's job coordinator, credited lead draftsman Bill Harper and Mike Ortbals, drafting-services manager, for the project's success.
"They provided drawings that were accurate to scale, and they were also there to answer questions and do follow-up if we had problems - for example, to redesign to meet our needs if what was on track was not working for us," Baldwin added.
Although three-quarters of the building Baldwin and other contractors worked on is new, MRB III also encapsulates an existing building that was gutted. It now houses 64 research laboratories, four teaching laboratories, support areas, conference rooms, classrooms and an 8,650-square-foot greenhouse.
The building's metal shingles, fluted fascia panels, ribbed panels and louvers were installed by R.D. Herbert & Sons Co., a Nashville roofing and sheet-metal contractor profiled in the July 2002 issue of SNIPS.
Local contractor Centex-Rodgers Inc., one of the largest health-care construction companies in the U.S, managed the project. It was completed in fall 2002.
(This article was supplied by Semco Inc.)