4.1601.1 Insulating Flex Ducts

Topic: 
Ducts
Subtopic: 
Insulating Ducts
Desired Outcome: 
Lower conductive heat transfer by ducts and decreased condensation on duct vapor barrier Vapor barrier A material that retards the passage of water vapor and contains a perm rating of less than 1
TitleSpecification(s)Objective(s)
4.1601.1a
Removal of existing flexible ducting

All accessible low R-value flexible ducting will be removed from premises

Ensure installation of proper R-value ducts

4.1601.1b
Selection of new flexible ducting

All flexible ducting will have a minimum of R-8

Minimize thermal conductance of the duct system

4.1601.1c
Sizing of new flex

Duct sizing procedures will be conducted when replacing flex duct

Improve comfort in rooms

Improve fan performance

4.1601.1d
Installation of flex

Flexible ducts will be supported in accordance with flex duct manufacturer's directions or local codes

Prevent sags, drops, or other bends that may interfere with correct air flow

4.1601.1e
Interior liner attachment

Interior liner of the flex-to-metal connection will be fastened with tie bands using a tie band Tie band A strap, often made of nylon, that mechanically squeezes a flexible duct to a fitting. Must have a minimum performance temperature rating of 165° (per UL 181A-type test) and a minimum tensile strength rating of 50 pounds tensioning tool or a mechanical band

Create a strong, secure attachment

4.1601.1f
Sealing of interior liner

Systems used to seal flexible air ducts and flexible air connectors will comply with UL UL Underwriters Laboratories 181B and will be marked "181 B-FX" for pressure- sensitive tape or "181 B-M" for mastic

Create an airtight connection

4.1601.1g
Attachment of exterior liner

Liner will be pulled up onto the metal duct as far as possible before securing

The exterior liner of the flex duct will be fastened with tie bands using a tie band Tie band A strap, often made of nylon, that mechanically squeezes a flexible duct to a fitting. Must have a minimum performance temperature rating of 165° (per UL 181A-type test) and a minimum tensile strength rating of 50 pounds tensioning tool

Create a strong, durable attachment

4.1601.1h
Sealing of all accessible ducts

All accessible joints, seams, and connections in ductwork will be securely fastened and sealed with UL UL Underwriters Laboratories "181 B-M" compliant mastic (adhesives) or mastic-plus-embedded-fabric systems

Minimize duct leakage

4.1601.1i
Insulation of all fittings

All metal fittings including boots, elbows, and take-offs will be insulated separately using an R-11 duct wrap with vapor retarder Vapor retarder A material that slows the passage of water vapor and contains a perm rating above 1

Minimize thermal conductance of the duct system

4.1601.1j
Completeness of vapor barrier Vapor barrier A material that retards the passage of water vapor and contains a perm rating of less than 1

Vapor retarder Vapor retarder A material that slows the passage of water vapor and contains a perm rating above 1 of all duct insulation will be taped to the flex duct using tape that complies with UL UL Underwriters Laboratories 181B and will be marked "181 B-FX" for pressure-sensitive tape or "181 B-M" for mastic

Ensure a complete vapor barrier Vapor barrier A material that retards the passage of water vapor and contains a perm rating of less than 1