HVAC equipment including air-handling units (AHUs)
and variable air volume (VAV) boxes will not be located in
close proximity to courtrooms, jury rooms, and chambers.
The minimum distance should be 7.6 meters (25 feet)
between AHU and courtrooms. (Refer to Chapter 5,
Theaters and Auditoriums, for criteria regarding maximum
duct velocity.) General system design needs to provide
appropriate treatment of mechanical supply/ return ducts
to minimize sound and voice transfer from courtroom,
chambers, jury deliberation spaces, witness rooms to
surrounding areas.
Noise criterion (NC), defines the limits that the octave
band spectrum of noise source must not exceed, should
range from 25-30 in U.S. Court facilities. For sound level
maintenance, the courtroom needs to be served by
constant volume air supply. The system must also support
variable outside air requirements and variable cooling
loads. Air ducts serving the trial jury and grand jury suites
must be double walled sound attenuating ducts for a
length of at least 12 feet from the diffuser or return air
Edward T. Gignoux U.S. Courthouse, Portland, ME
intake.
To control noise during all modes of operation and for all
Mechanical System Diffusers, Vents
load conditions, the HVAC system should be provided
Mechanical system diffusers and grills in public and staff
with one or more of the following:
areas will need to be secure from tampering, particularly
Sound traps and acoustic lining in the duct work;
in areas which provide some degree of seclusion and
Low-velocity, low static-pressure fan systems;
privacy (restrooms, attorney-client visitation rooms, etc.).
Maximum-security detention-type grilles, secured with
Special low-noise diffusers; and
tamper proof fasteners, shall be provided at all areas
Sound traps.
accessible to prisoners. (Refer to USMS-RSSPSSM for
If air is returned by the ceiling plenum, special attention
more information.)
should be given to the location of any partitions
extending to the floor structure above and to the
acoustical treatment of the required penetration of these
partitions for return air.
280 F A C I L I T I E S S T A N D A R D S
FOR THE
PUBLIC
BUILDINGS
SERVICE
9.5 Mechanical Systems
Revised March 2005 PBS-P100
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