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Mechanical / HVACaka: duct systemaka: air distribution systemaka: HVAC ducts

Ductwork

In Plain English

The system of sheet metal or flexible tubes that carries heated or cooled air throughout a building.

Definition

The network of conduits—typically sheet metal, fiberglass, or flexible material—that distributes conditioned air from the air handling unit to occupied spaces and returns air back to the unit. Ductwork is designed for proper airflow velocity, pressure drop, and noise levels. It must be sealed, insulated, and supported per code requirements.

Why It Matters in Bidding

Ductwork is typically the most labor-intensive portion of an HVAC bid, and sheet metal fabrication, hangers, sealing, and insulation are all separate cost drivers that estimators must capture from the mechanical plans. Because duct routing competes for ceiling space with plumbing, structure, and conduit, coordination assumptions made during bidding directly affect installed cost and the risk of field rework.

Example

An HVAC estimator takes off the supply and return ductwork by pound of galvanized sheet metal and linear foot of flex, adds external insulation and mastic sealing per the energy code, and carries extra labor for the tight congested corridor above the main lobby.

Related Terms

Air HandlerDiffuserDamperVariable Air Volume

Frequently Asked Questions

Sheet metal duct is commonly taken off by weight (pounds of metal) based on gauge and dimensions, while flex and round duct are measured by linear foot. Estimators add fittings, hangers, sealing, insulation, registers, and dampers, then apply fabrication and installation labor adjusted for ceiling height and congestion.
Labor is driven by duct gauge and size, the number of fittings and transitions, hanging height, working space congestion, and required sealing and insulation. Spiral and custom fabrication add shop time. Tight coordination with other trades above the ceiling can sharply increase install hours, so estimators factor jobsite conditions, not just quantities.
Yes. Energy codes commonly require sealed and insulated supply and return ducts, so estimators carry mastic or tape sealing labor and the insulation material and application as distinct line items. Leakage testing, where specified, is also a separate cost that must be picked up from the mechanical specifications.

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