No New Ducts Panned in Joists
No newly installed ducts are panned in floor joists — they must be fully ducted to prevent unintended air paths.
Spec
Applies uniformly from Silver upward.
Scope
Newly installed HVAC return-air ductwork in new construction.
Requirements
- 01.
No new HVAC return-air ducts may be "panned" — using the cavity between floor joists, capped with sheet metal, as the duct.
- 02.
All return-air ductwork must be fully ducted (rigid metal or insulated flex), sealed at every joint with UL-181 rated mastic or tape.
Documentation
Evidence the inspector / Institute will need.
- 01.
Photos of installed return-air ducts showing rigid or flex construction with sealed joints.
- 02.
Marked-up mechanical plan confirming no panned joist bays.
Guidance
Why panned joists fail
A panned joist bay relies on the floor framing as the duct surface — which means every gap in the framing (around nails, knockouts, end joints, plumbing penetrations) becomes a leak. Field studies consistently find 20-40% air leakage in panned-joist returns, which directly degrades HVAC efficiency and creates pressure imbalances that drive pollutants into the house from the basement/crawlspace.
Note
Existing panned-joist returns in renovation projects are not required to be removed — this Silver requirement applies to new ductwork only. At Platinum, all ducts (new + existing) must be fully ducted.