Quantity calculation and BOQ listing of ventilation ducts (supply/exhaust/fresh air): measurement is not split by system; listing splits by item characteristics (GB/T 50856-2024 Appendix G, code 030702)

Topic Positioning

This card answers a high-frequency HVAC BOQ question: are supply, exhaust, and fresh-air ducts computed and listed separately? Conclusion per GB/T 50856-2024 Appendix G, Table G.2.1 "fabrication and installation of ventilation ducts" (030702), its notes, and Clause 4.2.2 on codes.

Core Conclusions

Overall verdict: measurement rules unified (not split by system); BOQ listing and assembly split by item characteristics.

1. Measurement (supply, exhaust, fresh air all by developed area in m2 under one rule set):

• Developed area, without deducting inspection ports, measuring ports, supply and suction openings; excluding overlapping duct and mouth areas.
• Length by design centerline (main and branch divided at their centerline intersection), including elbows, tees, reducers, and rectangular-to-round adapters, excluding the lengths occupied by components.
• Tapered ducts: round by mean diameter; rectangular by mean perimeter.
• Wall-penetration sleeves computed by developed area and included in the corresponding duct quantities by material and thickness.

2. Listing (split):

• Table G.2.1 characteristics: name, material, shape, size, plate thickness, joint form, etc. (clean ducts add cleanliness class etc.); "name" is the system use (supply/exhaust/fresh air) — different names are different characteristics, hence separate items.
• Coding (Clause 4.2.2): codes are 12 digits; digits 1-9 per the appendix; 10-12 set from the project's item names and characteristics; no duplicate codes within the same unit works of one tender.
• Any differing characteristic — material, thickness, joint, size — requires separate listing; e.g., stainless smoke-exhaust ducts use the stainless-steel duct codes, not ordinary carbon-steel codes.

3. Assembly note: system differences show mainly in the "name" characteristic; match local sub-item tiers (usually by shape, material, thickness, joint, size) with unified measurement.

4. Other listing rules (Table G.2.1 notes): factory-made ducts listed under the corresponding duct items; where galvanizing of shaped steel in clean ducts is required, note it in work content; duct items include support/hanger fabrication and installation — if listed separately, use Appendix N codes.

5. Caliber analysis: length "excludes components" while area "does not deduct openings" are two different calibers — do not confuse; valves, diffusers, and silencers are separate items, not merged into duct quantities.

Applicable Boundaries

• Applies to HVAC BOQ compilation and measurement under GB/T 50856-2024; quota assembly per the project's local current edition.
• "Not split" means unified measurement only — not merged listing or merged assembly: any differing characteristic (name, material, shape, size, thickness, joint) must be listed and assembled separately.
• Clean, stainless, and factory-made ducts follow the corresponding Table G.2.1 note provisions (e.g., stainless smoke ducts under stainless codes).

Further Reading

• GB/T 50856-2024 Appendix G HVAC: Table G.2.1 (030702) and notes; Clause 4.2.2 (codes); Appendix N for separately listed supports.
• When checking tables, focus on the characteristics and calculation-rule columns; component (valve, diffuser, silencer) ownership should be confirmed against the corresponding component items.