TL;DR
A plenum is the sealed sheet-metal box attached directly to a furnace or air handler that distributes supply air into the duct branches or collects return air from them. The supply side sits on the equipment outlet and runs hottest, which is why codes require clearances there and why the air-conditioning evaporator coil usually lives inside it.
What it means
A plenum is the sealed sheet-metal box attached directly to a furnace or air handler that distributes supply air into the duct branches or collects return air from them. The supply side sits on the equipment outlet and runs hottest, which is why codes require clearances there and why the air-conditioning evaporator coil usually lives inside it. Leaky plenum joints waste more conditioned air than almost any other duct defect because system pressure peaks at that point.
Where it sits in the glossary
Plenum 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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