TL;DR
Flex duct is flexible air duct made of a wire helix supporting an inner plastic liner, wrapped in fiberglass insulation and a vapor-barrier jacket, sold in 25-foot bags in diameters from 4 to 20 inches. Quick and cheap for branch runs to registers, it punishes sloppy installation: sagging between supports, sharp bends, and excess compressed length multiply friction losses far beyond rigid metal equivalents.
What it means
Flex duct is flexible air duct made of a wire helix supporting an inner plastic liner, wrapped in fiberglass insulation and a vapor-barrier jacket, sold in 25-foot bags in diameters from 4 to 20 inches. Quick and cheap for branch runs to registers, it punishes sloppy installation: sagging between supports, sharp bends, and excess compressed length multiply friction losses far beyond rigid metal equivalents. Codes and ACCA Manual D require it pulled taut, supported every 4 feet, and cut to length rather than serpentined.
Where it sits in the glossary
Flex duct is part of the Trade jargon group inside the ProFix Directory glossary. Browse every term in this category from the glossary index.
Why Ohio homeowners should know it
This is a term Ohio homeowners encounter when reading contractor quotes, hiring paperwork, or inspection reports. Understanding it well enough to ask one good follow-up question is usually all the protection a homeowner needs.
ProFix Directory keeps definitions short on the index page and saves the longer context — Ohio-specific rules, where the term comes from, and which ProFix tools touch it — for these per-term pages so the term is easy to cite and easy to share.
ProFix tools that touch this term
See also
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