4.1601.5 Insulating Metal Ducts

Topic: 
Ducts
Subtopic: 
Insulating Ducts
Desired Outcome: 
Lowered thermal conductance of duct system and minimized condensation on the duct system
TitleSpecification(s)Objective(s)
4.1601.5a
Selection of duct insulation material

Duct insulation will be a minimum of R-8, in accordance with local code or buried under attic insulation, whichever is a greater R-value, and have an attached and continuous vapor barrier Vapor barrier A material that retards the passage of water vapor and contains a perm rating of less than 1

Hot humid and warm coastal regions will not bury ducts

Decrease heat loss and condensation problems
4.1601.5b
Duct sealing

All accessible ducts will be sealed with a UL UL Underwriters Laboratories -181 mastic before insulation is applied

Minimize duct leakage
4.1601.5c
Attachment of duct insulation

Duct insulation will be mechanically fastened (e.g., stitch staples, tie bands) and sealed with no exposed metal

Duct insulation will be secured to the duct system using metal wire or rot-proof nylon twine

Pattern of the wire or twine will be sufficient to securely hold the duct insulation tight to the duct

Mechanical fastening will be sufficient to securely hold the duct insulation in place and tight to the duct

Ensure a secure connection between the duct system and the duct insulation

Ensure performance of the installed material

Minimize condensation
4.1601.5d
Taping of the vapor barrier Vapor barrier A material that retards the passage of water vapor and contains a perm rating of less than 1

Using a tape approved by the manufacturer, all seams and connection of the vapor barrier Vapor barrier A material that retards the passage of water vapor and contains a perm rating of less than 1 will be taped so that no metal is exposed

No gaps will exist between pieces of duct insulation

Prevent gaps in the vapor barrier Vapor barrier A material that retards the passage of water vapor and contains a perm rating of less than 1 of the insulation
4.1601.5e
Vermin proofing

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

Ensure long-term durability of the building materials