HVAC Procedure and Performance Guide

TASK: Install main duct (rectangular rigid fiberglass) and fittings.

Training for this procedure can be found in these courses:

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


Main duct (rectangular rigid fiberglass) and fittings must be installed according to manufacturer’s specifications, job specifications and codes.  Duct joints and seams must not leak.  Applicable safety procedures must be followed.


  1. Review manufacturer’s specifications, job specifications and codes.
  2. Collect tools, equipment and materials.
  3. Put on safety and protective equipment and apparel.
  4. Determine duct size and routing from specifications.
  5. Prepare duct penetration.
  6. Cut duct board and kerf for folding and end connections.
  7. Form duct board into specified rectangular sections.
    • Fold duct board at kerfs.
    • Staple foil overlap.
    • Seal seam.
    • Install metal reinforcement on large sections.

8. Connect duct sections and fittings.

    • Begin at fan discharge or takeoff and continue to end of duct.
    • b. Install supports as needed.
    • c. Fabricate fittings required from duct board or use metal fittings.
    • d. Cap end of main duct.

9. Install takeoffs.

    •  Locate takeoffs according to specifications.
    • b. Select appropriate metal duct board adaptable fittings (tab collar or twist collar with or without damper).
    • c. Cut opening and select fitting.
    • d. Install fitting.

10. Insulate metal fitting if applicable.

11. Remove safety and protective equipment and apparel.

12. Gather tools, equipment and leftover materials and leave work site clean.