HVAC Procedure and Performance Guide

TASK: Install duct (round flexible fiberglass) and fittings.

Training for this procedure can be found in these courses:

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


Round flexible fiberglass duct and fittings must be installed according to manufacturer’s specifications and job specifications.  Duct joints must be tight with minimum air leakage and must not collapse in bends.  Applicable safety procedures must be followed.


  1. Review manufacturer’s specifications and job specifications.
  2. Collect tools, equipment and materials.
  3. Put on safety and protective equipment and apparel.
  4. Determine duct size and routing.
  5. Prepare duct penetration and register openings.
  6. Connect duct section to unit air supply or branch takeoff fitting using flexible duct clamp.  (Note:  Install short metal section containing balancing damper or spin-in with scoop and damper at branch takeoffs from main).
  7. Lay out duct along routing and install supports.  (Note:  Avoid excessive slack in duct.  Install metal elbows in tight bends to prevent duct collapse).
  8. Make duct connections using manufacturer’s recommended overlap and duct tape.
  9. Make duct connections to metal fittings using flexible duct clamps (panduit straps).  (Note:  Position duct clamps so they do not interfere with action of damper arms).
  10. Install stack head, register box or register boot.
  11. Insulate metal fittings.
  12. Remove safety and protective equipment and apparel.
  13. Gather tools, equipment and leftover materials and leave work site clean.