4.1601.3 Insulation and Vapor Barrier

Topic: 
Ducts
Subtopic: 
Insulating Ducts
For supporting material, see Building America Solution Center.
Desired Outcome: 
Minimize condensation
TitleSpecification(s)Objective(s)
4.1601.3a
Ducts in unconditioned spaces (e.g., crawl space, attic, unconditioned basements)

Ducts will have continuous insulation and vapor barrier Vapor barrier A material that retards the passage of water vapor and contains a perm rating of less than 1

Insulation will be sufficient to prevent dew point on surface of ducts

Minimize condensation

4.1601.3b
Ducts within floor assemblies

Inspection and/or testing will be conducted to determine whether ducts are within thermal, pressure, and vapor boundary

If ducts are within thermal, pressure, and vapor boundary, no action will be required

If ducts are not within thermal, pressure, and vapor boundary, continuous air barrier Air barrier The separation between the interior and exterior environments of a building that slows air flow to the point that no smoke movement is visible at 50 pascals of pressure difference across the boundary , insulation, and vapor retarder Vapor retarder A material that slows the passage of water vapor and contains a perm rating above 1 will be installed either on the ducts or at the belly liner

Minimize condensation

4.1601.3c
Exposed metal

All exposed metal will have continuous insulation and vapor retarder Vapor retarder A material that slows the passage of water vapor and contains a perm rating above 1

Minimize condensation