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Underfloor air distribution (UFAD) systems require good coordination between
all building trades throughout the design and construction process. Shute
(1995) provides an excellent list of recommendations for the design and
construction of underfloor air distribution systems. McCarry (1995) also
describes some guidelines based on his experiences with UFAD system
installation. More recently, Bauman (2003) discusses guidelines for a
well-coordinated construction sequence. Shown below is a partial list of
recommendations for design and construction.
is essential that the implications of the raised access floor be considered
early in the design process.
concrete slab surface must be sealed to reduce dust, and the underfloor
plenum and floor panels must be thoroughly cleaned both during installation
of the access floor and again before occupancy.
height of the access floor and the placement of the 0.6 m x 0.6 m (2 ft x 2
ft) raised floor pedestal grid is critical with respect to locating all
underfloor service installations.
is important to lay out underfloor equipment requiring regular maintenance
to be located in accessible areas, such as corridors, not underneath
furniture and partitions.
partitioned office spaces, offset the partition grid from the floor grid so
that partitions do not cover joints between floor panels, thereby preventing
access to the underfloor plenum on both sides of the partition.
dead load allowance and seismic bracing of the access floor.
areas in the building with no access floor and allow for transitions to
areas with access flooring.
pressurized underfloor air distribution systems, greater care must be taken
during construction to seal the underfloor plenum to prevent uncontrolled
- Designers must
consider that fan rooms or access for HVAC distribution will be required at
more frequent intervals than with conventional air distribution systems.
- If called for,
return air shafts must be designed between the ceiling and the underfloor
plenum, usually around columns or other permanent building elements.
- The main
structural slab, the traditional working platform, will not be available
continuously during construction, and therefore a well coordinated
construction sequence is necessary (see Shute 1995).
F. 2003. Underfloor air distribution (UFAD) design guide. Atlanta:
 McCarry, B.T. 1995. Underfloor air distribution systems: Benefits and when
to use the system in building design. ASHRAE Transactions 101 (pt. 2).
 Shute, R.W. 1995. Integrated access floor HVAC:
Lessons learned. ASHRAE Transactions 101 (pt. 2).