"In order to expose the structure of the building for increased aesthetic value, to provide the tenant with exceptional flexibility, and provide a greater floor-to-floor height for better lighting solutions, we decided to propose a raised-floor hvac system," says David Rezac, project manager with CDFM2.

Bill Fagan, executive vice president of sales for The Fagan Co.-Comfort Systems USA, the mechanical contractor selected for the job, agreed with Rezac's recommendation. "We suggest raised floor hvac systems for clients with high-technology environments and a significant amount of (employee) churn," said Fagan. DST fit these criteria perfectly, so a York FlexSys underfloor-air system was selected to deliver conditioned air to the 76,000-sq-ft building.

Because raised-floor hvac systems eliminate overhead ductwork, CDFM2 was able to preserve the historic nature of the building by exposing existing ceilings, as well as create a unique, new second floor in the middle of the building. What had been a two-story structure was converted into three floors of modern office space.

In addition, the second-floor slab for the new floor was stopped short of the perimeter wall, creating a dynamic space in the main lobby. Skylights and new openings through the second floor bring natural light into the building. All of this, along with the FlexSys system, transformed the 1920s, two-story warehouse into a three-story, technology-ready office building.

Being Underfoot Has Its Advantages

Tom Corso, operations manager for M.C. Real Estate Services, which manages the building, was pleased that the installation of the FlexSys system resulted in a 10% budget decrease in building renovation costs.

The FlexSys system offers users first-cost and life-cycle cost savings. Because air moves in the plenum between the structural floor and the access floor, conventional ceiling ductwork can be eliminated. This saves installation costs and frees overhead space for other design purposes. Office rearrangement costs are reduced also. A FlexSys terminal can be installed literally anywhere in the raised-floor grid, because the entire area under the floor becomes a pressurized air plenum.

For DST's building, four 40-ton York rooftop hvac units provide air to the pressurized plenum. The entire system is variable-air volume (vav), for precise comfort control and optimum energy savings.

To reconfigure workstations, maintenance personnel simply remove one or two access floor panels to relocate voice, data, and power cabling. Then, they can move the air terminals, bringing conditioned air to the reconfigured space as needed. This can be done much more quickly and at less expense than with traditional building systems.

"I think the aspect of the system we are most pleased with is the comfort level in the working environment," says Corso. Because the air is not blown from overhead, where pollutants gather, FlexSys also provides improved IAQ. Of all the buildings he manages, Corso receives the fewest occupant complaints from DST.

Raised-Floor Systems Rising

Installation of FlexSys systems often is less complicated than other hvac systems, in large part because ductwork is eliminated. However, close coordination is required among contractors and subcontractors to ensure proper installation and superior air quality.

"The floor has to be airtight for an underfloor hvac system to operate properly, and the area must be free of construction debris," notes Fagan. "This was a design-build system, and York was very responsive," he adds.

Fagan says that about 20% of the building projects he works on implement an underfloor hvac system, and he believes that number will increase. "Customers are requiring more and more wiring for high-tech systems, as well as changing office areas more frequently. Raised-floors with systems like FlexSys are an economical, space-saving alternative to conventional hvac systems." ES