4.1601.4 Insulating Flex Ducts

Topic: 
Ducts
Subtopic: 
Insulating Ducts
Desired Outcome: 
Lower conductive heat transfer by ducts and decrease 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)
4.1601.4a
Removal of existing flexible ducting

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

Ensure installation of proper R-value ducts

4.1601.4b
Selection of new flexible ducting

All flexible ducting will have a minimum of R-8

Minimize thermal conductance through the duct system

4.1601.4c
Sizing of new flex

Duct-sizing procedures will be conducted when replacing flex duct

Improve comfort in rooms

Improve fan performance

4.1601.4d
Installation of flex

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

Beaded rigid elbow or equivalent will be installed in duct runs whenever change in direction is required

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

Maintain duct diameter around the turns

Maximize air flow and distribution

4.1601.4e
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

For oval flexible duct-to-metal connections, tie bands cannot be used; appropriate mechanical fasteners will be used

Create a strong, secure attachment

4.1601.4f
Sealing of interior liner

UL UL Underwriters Laboratories 181 B-M-listed mastic product will be used to seal the connection

Create an airtight connection

4.1601.4g
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

4.1601.4h
Sealing of all accessible ducts

All accessible joints, seams, and connections will be sealed with UL UL Underwriters Laboratories 181 approved mastics

Minimize duct leakage

4.1601.4i
Insulation of all fittings

All metal fittings, including boots, elbows, and takeoffs, will be insulated separately using a minimum of R-8 duct wrap with a vapor barrier Vapor barrier A material that retards the passage of water vapor and contains a perm rating of less than 1 mechanically fastened (e.g., stitch staples, tie bands) and sealed with no exposed metal

Minimize thermal conductance of the duct system

Minimize condensation

4.1601.4j
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 barrier Vapor barrier A material that retards the passage of water vapor and contains a perm rating of less than 1 of all duct insulation will be taped to the flex duct using the taping system required by the manufacturer of the duct insulation

Vapor barrier Vapor barrier A material that retards the passage of water vapor and contains a perm rating of less than 1 will be sealed to the belly liner

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

4.1601.4k
Vermin proofing

Vermin access points will be identified and treated appropriately (e.g., seal access holes)

Ensure long-term durability of the building materials

4.1601.4l
CAZ CAZ Combustion appliance zone testing

CAZ CAZ Combustion appliance zone testing will be performed where combustion appliances are utilized

Identify unsafe equipment operating conditions