Segregating lab and non-lab systems is one possibility, but that works only in buildings with easily segregated functions. The new paradigm, however, is for various functions to share the same spaces or to be interspersed throughout the building, says Paul Pohlod, principal engineer at Burt Hill architectural and engineering firm.

A more viable and efficient solution is to create a central air handling system for the entire building, and mix and match the components for intake, exhaust, and heat recovery. A common duct system supplies air to all the spaces; 100 percent of the lab air must be exhausted; 100 percent of the return air from the non-lab spaces is used to pre-treat the air that serves the entire building. The combination of recirculated air and application of energy recovery is used to moderate the intake air conditions from a range of 91 degrees in summer to –5 degrees in winter, to a range between 81 and 36 degrees resulting in energy efficiency improvements of as much as 28 percent.

“By using this one common system, we are delivering about 80 percent outside air to the entire facility, instead of 20 percent to the non-lab functions and 100 percent to the labs,” says Pohlod.

The efficiency can be further improved by adding features such as occupancy sensors and by utilizing an extended plenum air distribution system.

In a traditional system, the duct system is designed specifically for the anticipated occupancy of each space, so it decreases in sized as it goes through the system. With the extended plenum, the duct work is of a consistent size throughout the floor plate, which allows for adaptation with changing occupancies and air flow rates. It also reduces the air velocity—and therefore the noise and static pressure—in the ductwork, which increases energy efficiency.

“You pay a premium of about 20 percent in the initial duct construction, but you get eight percent energy savings and enhanced flexibility in the future,” he says.

Flexibility is a goal in the electrical service and casework, as well. The traditional surface metal “raceway” delivery system with piped electrical services in the ceiling plenum is one of the least expensive, at about $140/linear foot of bench, but it was designed for fixed casework and offers no flexibility in the future. Other options can cost several times more, but offer more flexibility: field wired utility columns, overhead service carriers, pre-wired utility columns, and an overhead power busway.

A renovation cost comparison on flexible vs. fixed casework generated similar results:

1. Fixed benches, fixed casework, piped services: $220/sf (renovated square feet, broken into the architectural, structural, mechanical, electrical, and plumbing, separate from the benches, casework, and equipment)
2. Moveable benches, mobile casework, overhead service column: $227/sf
3. Moveable benches, mobile casework, overhead service carrier: $267/sf

Interdisciplinary buildings need frequent reconfiguration, so while designing for greater flexibility may cost more upfront, it will save money in the long term.

L.W.