15 May 2003
Use either the Static Regain or the T-Method method to design ducts for VAV
systems. Use round and oval prefabricated duct wherever possible to reduce both
leakage and friction losses. The additional material cost for round or oval prefabricated
duct is often offset by reduced installation cost and time and reduced fan energy
consumption and air leakage. Note that the use of oval ductwork is sometimes
restricted to positive pressure applications.
Ensure that duct design incorporates all features necessary to accommodate
testing, adjusting, and balancing (TAB). For example, provide adequate length of duct,
both upstream and downstream of fans and coils. Show the necessary fittings,
transitions, test ports, etc. required for successful TAB, for duct inspection and cleaning,
and for damper access and inspection.
Do not use the following types of construction where the potential for
subterranean termite infestation is high:
Sub-slab or intra-slab HVAC ducts.
Plenum-type, subfloor HVAC systems, as currently defined in Federal Housing
Administration minimum acceptable construction criteria guidance.
HVAC ducts in enclosed crawl spaces that are exposed to the ground.
HVAC systems where any part of the ducting is in contact with or exposed to the
. Provisions for the prevention and mitigation
of indoor radon will
comply with UFC 3-490-04A Indoor Radon Prevention and Mitigation.
CONTROLS. Design HVAC controls in accordance with UFGS 23 09 23
Direct Digital Control for HVAC and Other local Building Systems and UFGS 25 10 10
Utility Monitoring and Control Systems (UMCS).
SEISMIC PROTECTION. Design HVAC systems with respect to seismic
protection in accordance with the International Building Code.
TESTING, ADJUSTING, AND BALANCING. UFGS 23 05 93.00 10 Testing,
Adjusting, and Balancing of HVAC Systems contains many of the requirements of
HVAC testing, adjusting, and balancing including strict quality control guidelines that the
construction contractor must meet in order to verify that the HVAC systems have been
properly installed and operating as specified. All features required for successful TAB
must be shown on the design drawings.
HVAC Systems is mandatory for all Army and Air Force projects. Note that use of