Read the spec first
Start with Division 23. Read 23 31 13 for metal ducts. It sets the pressure class, the sealing and the gauge. Read 23 09 00 for controls and 23 05 93 for testing, adjusting and balancing. Read the insulation section. Note what the spec says about duct liner.
Sheets and schedules that carry the count
- The equipment schedules: rooftop units, air handlers, terminal units, fans and pumps.
- The air device schedule: diffusers, grilles and registers by tag.
- The duct plans on the M sheets.
- The piping plans and the flow diagrams.
- The roof plan. It shows curbs and openings.
- The life safety plan. It shows the rated walls that need dampers.
Steps in order
- List each piece of equipment from the schedules.
- Find each tag on the plans. Note any tag you cannot find.
- Count air devices by tag.
- Measure duct by size and by pressure class. Count the fittings.
- Measure flexible duct and count the terminal unit connections.
- Measure hydronic and refrigerant pipe by size. Count the valves.
- Count fire and smoke dampers where duct crosses a rated wall.
- Add insulation, hangers, controls and balancing.
Count, length, area or volume
- Count: equipment, air devices, dampers, valves and control points.
- Length: duct by size, pipe by size and flexible duct.
- Area: sheet metal surface and duct insulation. Many shops convert duct to weight.
- Volume: seldom used.
Conflicts to find, and what to exclude
- The schedule lists a quantity. The plans show a different number of tags.
- The spec calls for external wrap. A drawing note calls for liner.
- Rated walls cross the duct, but the M sheets show no dampers.
- Nobody states who supplies roof curbs and who cuts the roof openings.
- Controls appear in Division 23 and again in a separate controls section.
State who supplies starters, disconnects and control wiring. Qualify crane time, structural supports and roof patching. Exclude line voltage power. Exclude condensate drains only if the plumber carries them in writing.
Trade takeoffs · Updated 11 Nov 2026