C403.2.9 Duct and Plenum Insulation, Construction and Sealing (Mandatory)
|Exterior of building||R-6||R-4.2|
|Unvented attic above insulated ceiling||R-6||R-4.2|
|Unvented attic with roof insulation||R-4.2||None|
|Indirectly conditioned spacesb||None||None|
All ducts, air handlers, filter boxes, building cavities, mechanical closets and enclosed support platforms that form the primary air containment passageways for air distribution systems shall be considered ducts or plenum chambers and shall be constructed and erected in accordance with Table C403.2.9.2 and with Chapter 6 of the Florida Building Code, Mechanical. Ducts shall be constructed, braced, reinforced and installed to provide structural strength and durability. All transverse joints, longitudinal seams and fitting connections shall be securely fastened in accordance with the applicable standards of this section.
DUCT SYSTEM CONSTRUCTION AND SEALING
|DUCT TYPE/ |
|SEALING REQUIREMENTS||MECHANICAL ATTACHMENT||TEST STANDARD|
|Metal duct, rigid and |
|Pressures less than 1- |
inch water gauge
|Closure systems as described in ||Mechanical attachments approved: ||SMACNA HVAC Air Duct Leakage Test Manual|
|Pressures 1-inch water |
gauge or greater
|Closure systems as described in ||Mechanical attachments approved: |
Continuous welds.Round metal ducts shall be
mechanically fastened by means ofat least three sheet-metal screws or
rivets equally spaced around the joint.a
|SMACNA HVAC Air Duct Leakage Test Manual|
|High-pressure duct systems |
designed to operate atpressures greater than 3-inch
water gauge (4-inch watergauge pressure class)
|The tested duct leakage class, at a test pressure |
equal to the design ductpressure class rating, shall be equal to
or less than Leakage Class 6. Leakagetesting may be limited to representative
sections of the duct system but in nocase shall such tested sections include
less than 25 percent of the totalinstalled duct area for the designated pressure class.
|SMACNA HVAC Air Duct Leakage Test Manual|
|Plastic duct||See Section 603.8.3 of the Florida Building Code, Mechanical.||Joints between plastic ducts and plastic |
fittings shall be made in accordance with
the manufacturer's installation instructions.
|Fibrous glass duct, rigid||All joints, seams and duct wall |
penetrations between sections of ductand between duct and other distribution
system components shall be sealed withclosure systems as described in
|Mechanically fastened per standard to |
secure the sections independent of theclosure system(s).
|NAIMA Fibrous Glass Duct Construction Standards.|
|Attachments of ductwork to air-handling |
equipment shall be by mechanicalfasteners. Where access is limited, two
fasteners on one side shall be acceptable.
|UL 181 |
|Flexible duct systems, nonmetal||All duct collar fittings shall have a |
minimum 5/8-inch (16 mm) integralflange for sealing to other components
and a minimum 3-inch (76 mm) shaftfor insertion into the inner duct core.
|Flexible nonmetal ducts shall be joined |
to all other air distribution systemcomponents by either terminal or
|UL 181 |
|Flexible ducts having porous inner |
cores shall not be used.
Exception: Ducts having a
nonporous liner between the porousinner core and the outer jacket.
Fastening and sealing requirementsshall be applied to such intermediate liners.
|Mechanical fasteners for use with |
flexible nonmetallic air ducts shallcomply with UL 181B and shall be
|See Section 603.10 of the Florida Building Code, Mechanical, for duct |
|Duct core to duct fitting||The reinforced lining shall be sealed to the duct |
fitting using one of the following sealingmaterials, which conforms to the approved
closure and mechanical attachment requirementsof Section C403.2.9.3:
|The reinforced core shall be mechanically |
mm) into each section of duct core. Whenthe flexible duct is larger than 12 inches
(303 mm) in diameter or the designpressure exceeds 1-inch water gauge, the
drawband shall be secured by a raised beador indented groove on the fitting.
|Duct outer jacket to |
duct collar fitting
|The outer jacket of a flexible duct section shall |
be secured at the juncture of the air distributionsystem component and intermediate or terminal
fitting in such a way as to prevent excesscondensation. The outer jacket of a flexible duct section shall not be interposed between the flange of the duct fitting and the flexible duct, rigid fibrous glass duct board or sheet metal to which it is mated.
|Duct collar fitting to rigid duct||The duct collar fitting's integral flange shall be |
sealed to the rigid duct board or sheet metalusing one of the following closure
systems/materials, which conforms to theapproved closure and mechanical attachment
standards of Section C403.2.9.3:
|The duct collar fitting shall be |
mechanically attached to the rigid ductboard or sheet metal by appropriate
mechanical fasteners, either screws,spin-in flanges or dovetail flanges.
|Terminal and intermediate |
|Approved closure systems shall be as designated |
by air distribution system component materialtype in Section C403.2.9.3.
|Fittings and joints between |
dissimilar duct types
|Terminal fittings and |
air ducts to buildingenvelope components
|Terminal fittings and air ducts that penetrate |
the building envelope shall be mechanicallyattached to the structure and sealed to the
envelope component penetrated and shall useone of the following closure systems/materials
which conform to the approved closure andmechanical application requirements of
|Air-handling units||Air-handling units located outside the |
for metallic ducts.
|All air-handling units shall be |
mechanically attached to other airdistribution system components.
|Return plenums||Building cavities that will be used as return air |
plenums shall be lined with a continuous airbarrier made of durable nonporous materials. All
penetrations to the air barrier shall be sealed witha suitable long-life mastic material. Roof decks above building cavities used as a
return air plenum shall be insulated to at leastR-19.
|Mechanical closets||All joints between the air barriers of walls, |
ceiling, floor and door framing and allpenetrations of the air barrier shall be sealed to wall, through-floor and through-ceiling
air passageways into the closet shall be framedand sealed to form an air-tight passageway.
Exception: Air passageways into the closet from conditioned space that are specifically designed for return airflow.The following air barriers are approved for use in mechanical closets:
|Enclosed support platforms in |
|Enclosed support platforms located between the |
return air inlet(s) from conditioned space and theinlet of the air-handling unit or furnace, shall
contain a duct section constructed entirely of rigidmetal, rigid fibrous glass duct board or flexible
duct, which is constructed and sealed according tothe respective requirements of Section C403.2.9.2
and insulated according to the requirements ofSection C403.2.9.1.
|The branch duct shall be fabricated and |
attached to the duct insert in accordancewith requirements for the duct type used.
Sufficient space shall be provided adjacent to all mechanical components located in or forming a part of the air distribution system to assure adequate access for: (1) construction and sealing in accordance with the requirements of Section C403.2.9, (2) inspection and (3) cleaning and maintenance. A minimum of 4 inches (102 mm) is considered sufficient space around air-handling units.