Attachment 3. MAHG231012 Clean Ductwork _Appx B-FLEXIBLE HVAC.pdf
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- Attached to
- MAHG 23-1012 Lott Hall HVAC Cleaning
- Solicitation number
- FA301025R0013
About this file
This document is a Statement of Work (SOW) Appendix B detailing specifications and installation requirements for insulated flexible air ducts for a ductwork cleaning project at Trent Lott Hall B2603 at Keesler Air Force Base. The specification provides comprehensive technical requirements for flexible ducts, including material composition (helical wound spring wire steel with 2" thick R6 minimum fibrous-glass insulation), performance standards (conforming to NFPA 90A/B, UL181A/B), and specific installation guidelines such as maximum support intervals of 4 feet, minimum bend radius requirements, and avoiding contact with hot equipment.
The document specifies that the flexible duct must have a maximum flame spread index of 25, a smoke developed index of 50, and include a fire-retardant jacket with an integral vapor barrier. Installation instructions emphasize avoiding compressed states, minimizing duct sagging, and maintaining proper support to prevent airflow restrictions. The specification anticipates that approximately 20% of the flexible ductwork may require replacement during the project, and provides detailed guidance on repair, support, and connection methods to ensure proper installation and performance.
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SOW Appendix B MAHG231012, Trent Lott Hall B2603, Duct Cleaning
INSULATED FLEXIBLE DUCT SPECIFICATION
• SPECIFICATION OF INSULATED FLEXIBLE DUCTS:
o Flexible duct must conform with NFPA 90A/B, UL181A/B and install in air systems of
SMACNA Low Pressure Duct construction standards (<2”wc, <2000fpm) and air system temperatures shall operate between -20—250degF.
o Flexible duct must fabricate per ASTM C553, with helical wound, spring wire steel and 2” thick R6 minimum fibrous-glass insulation with factory applied film vapor barrier and acoustic requirement of NRC 0.65.
Similar or equal to Thermaflex Pro Series M-KC flexible air duct @ 2”thick R6.0, with 8” inside bend radius. Shipped in 25ft lengths, to be cut into 5ft lengths max. for install.
o Provide CFC and HCFC free flexible duct insulation.
o Flexible duct insulation must have a maximum flame spread index of 25 and a maximum smoke developed index of 50 per ASTM E84 and UL 723 testing.
o Provide insulation with insulation manufacturer's standard reinforced fire-retardant jacket with integral vapor barrier. Insulation exterior shall be cleanable, grease resistant, non-flaking and non-peeling.
o Vapor barrier/weatherproofing jacket shall be laminated self-adhesive (min. 2 mils adhesive, 3mils embossed) less than 0.05 perms.
o Flexible duct insulation materials shall be compatible and shall not contribute to corrosion, soften, or otherwise attack surfaces to which applied in either wet or dry state.
o Flexible duct sections shall have 20oz. glass fabric duct connectors coated with neoprene on both sides.
o Do not allow flexible duct insulation to get wet. Any “wetted” flexible duct shall NOT be used for construction. Do not store flexible duct in sunlight. Vapor barrier will deteriorate when exposed to sunlight. Contractor shall take steps to protect flexible duct from exposure to the weather during delivery and as stored on job site.
o All connections, joints and splices shall be made in accordance with the manufacturer’s installation instructions. Sheet metal fittings to which flexible ducts with plain ends are attached shall be beaded and have a minimum of 2 inches collar length. Beads are optional for fittings when using metal worm-gear clamps or when attaching metallic flexible ducts using sheet metal screws.
o All tapes, mastics, and nonmetallic clamps used for field installation of flexible ducts shall be listed and labeled to Standard UL 181B - Closure Systems for Use with Flexible Air Ducts and Air Connectors.
o Connections and Splices with either metallic or non-metallic plain ends shall be made up per ADC-IR5E, Flexible Duct Installation Standards Para 4.7.1, 4.7.2, and 4.7.3.
FA301024R0010
Attachment 3.
SOW Appendix B MAHG231012, Trent Lott Hall B2603, Duct Cleaning
INSULATED FLEXIBLE DUCT SPECIFICATION
• INSTALLATION OF INSULATED FLEXIBLE DUCTS:
o Terminal devices shall be supported independently of the flexible duct.
o Repair torn or damaged vapor barrier/jacket with duct tape listed and labeled to
Standard UL 181B. If internal core is penetrated, replace flexible duct or treat as a connection.
o Install ducts fully extended. Do not install in the compressed state or use excess length as this will noticeably increase friction losses.
o Care shall be taken to minimize sagging or snaking of the duct between supports and minimize pressure loss caused by excessive direction changes to the airflow.
o Do not bend ducts across a sharp corner of building materials such as joists or truss supports. The bend radius at the center line of ducts shall be equal to or greater than one duct diameter. Sharp bends increase pressure drop significantly and reduce airflow.
o Avoid incidental contact with metal fixtures, water lines, pipes, or conduits. Do not install near hot equipment or piping (e.g. furnaces, boilers, steam pipes, etc.) that is above the 250degF.
o Duct Supports: Flexible duct shall be supported at manufacturer’s recommended intervals, but at no greater distance than 4 feet. Supporting shall be provided so that the maximum centerline sag is 1/2" per foot of spacing between supports. A connection to rigid duct or equipment may be considered a support joint.
o Long horizontal duct runs with sharp bends shall have additional supports before and after the bend approximately one duct diameter from the center line of the bend.
o Hanger or saddle material in contact with the flexible duct shall be of sufficient width to prevent any restriction of the internal diameter of the duct when the weight of the supported section rests on the hanger or saddle material. In no case will the material contacting the flexible duct be less than 1-1/2” wide. Care shall be taken to ensure the vapor barrier and insulation material are not excessively compressed by the support straps. Compressing the insulation could lead to condensation at the point of contact between the duct and the strap or saddle material.
o Support the duct between a metal connection and bend by allowing the duct to extend straight for at least one duct diameter before making the bend. This will avoid possible damage of the flexible duct by the edge of the metal collar and allow for efficient air flow and fitting performance.
o Assume 20% of flexible ductwork is damaged and requires replacement.
FA301024R0010
Attachment 3.
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