3.1602.9 Crossover Ducts

Topic: 
Ducts
Subtopic: 
Duct Sealing
Desired Outcome: 
Deliver all air from trunk to trunk without leakage or restriction
TitleSpecification(s)Objective(s)
3.1602.9a
Work assessment

Installer prework assessment will be conducted to determine:

  • Location
  • Types
  • Leakage points

Verify scope of work

3.1602.9b
Flexible crossover duct connections

Flexible crossover duct connections will be added, rebuilt, or repaired using compatible materials and will be:

  • Mechanically fastened at both inner and outer liner
  • Sealed using UL UL Underwriters Laboratories -listed sealant that is durable, structurally sound, insulated
  • Equipped with a vapor retarder Vapor retarder A material that slows the passage of water vapor and contains a perm rating above 1

Whenever possible, rigid elbow or equivalent will be installed in crawl space crossover ducts

Floor insulation will be in contact with the outer liner of the crossover duct

Crossover duct vapor retarder Vapor retarder A material that slows the passage of water vapor and contains a perm rating above 1 will be sealed to the bottom liner (e.g., belly fabric)

New flex duct installation will be insulated to a minimum of R-8

When feasible, 26-gauge hard duct should be installed

If a new crossover is required, it must be insulated to at least R-8 and be air sealed

Ensure lasting durable connections

Minimize air leakage and heat transfer

Maintain duct diameter around the turns

Maximize air flow and distribution

3.1602.9c
Support

Crossover ducts will be installed so they are not in contact with the ground

Crossover ducts will be supported in accordance with flex duct manufacturer specifications, local codes

Support materials will be applied in accordance with manufacturer specifications for interior dimensions and will not crimp ductwork, dip, or sag

Maximize air flow and distribution

Minimize condensation

Minimize air leakage and heat transfer

3.1602.9d
Through-the-rim crossover duct

Through-the-rim crossover ducts will be located and accessed through the bottom liner and branch duct; all branch crossover duct connections and end caps will be located and accessed

Hole size (air pathway) will be maximized between branch crossover and trunk

All connections will be mechanically fastened and sealed inside duct

End caps will be sealed

Ensure all connections are identified

Maximize air flow and distribution

Ensure lasting durable connections

Minimize air leakage

3.1602.9e
Repair work access for through-the-rim crossover

Access hole in the trunk duct will be repaired and sealed

Insulation will be reinstalled

Bottom liner/belly will be repaired

Repair work access

Minimize heat transfer

3.1602.9f
Attic crossover

Access to the attic will be created for all attic areas that contain crossover ducts, where feasible

Plenum boxes and crossover duct connections will be rebuilt, mechanically fastened, and sealed

Access holes will be repaired

Ensure lasting durable connections

Minimize air leakage

Maximize air flow and distribution

Repair work access

3.1602.9g
Combustion Appliance Zone ( 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

3.1602.9h
Performance testing

Pre- and post-retrofit duct leakage will be performance tested using a duct blaster or pressure pan, and results will be documented and reported to the homeowner and/or program

Document post-retrofit duct leakage test has been performed