HVAC Procedure and Performance Guide

TASK: Install duct (rectangular metal) and fittings

Training for this procedure can be found in these courses:

                         103 – Basic Sheet Metal  and  205 – HVACR High Efficiency Ventilation


Duct and fittings must be installed according to job specifications.  Duct joints must be tight with minimum air leakage and duct noise.  Applicable safety procedures must be followed.


  1. Review job specifications.
  2. Collect tools, equipment and materials.
  3. Put on safety and protective equipment and apparel.
  4. Fit longitudinal seams of duct sections together to form rectangular duct.
  5. Prepare duct penetrations and register openings.
  6. Install main (trunk) duct
    • Determine duct size, type of duct connector required (S cleat, drive cleat, snap, etc.) and routing.
    • Install flexible connector on air-handling unit discharge.
    • Cut duct sections as needed and compare ends for connections.
    • Cut connectors to correct lengths for duct sizes.
    • Install duct connections, beginning at flexible connector and continuing assembly to end of run, using necessary reducers, elbows and duct hangers.
    • Cap end of main duct.
  7. Install branch duct from main:
    • Locate takeoff point and determine size of takeoff branch.
    • Mark center of the takeoff point, scribe opening and cut opening in main.
    • Insert takeoff fitting and secure, using fitting tabs or sheet metal screws.
    • Install manual balancing damper in duct section.
    • Connect duct section to takeoff.
    • Connect remaining duct sections to register location.
    • Install stack heads, register box or register boot.Install duct insulation.
  8. Install duct insulation.
  9. Remove safety and protective equipment and apparel.
  10. Gather tools, equipment and leftover materials and leave work site clean.