A Flexible Duct Was Knocked Loose From a Heat Vent

Flexible Duct

• Flexible duct is made of plastic that is stretched over wire coil. It is insulated with fiberglass to prevent heating or cooling loss. Flexible duct is lighter, easier to work with and less expensive than rigid duct. It is also more prone to being knocked loose by careless workers.

Boot

• Flexible duct attaches to the collar end of an HVAC unit's register boot while the register, or vent, end is nailed either between two wall studs or two floor/ceiling joists. Because boots are stiff and stationary, they are seldom the cause of flexible duct being knocked loose; however, their lack of flexibility is often a contributing factor in disconnections. The boot won't move, so any significant pressure will knock the flexible duct away. Always nail boots into place before attaching the flexible duct work.

Adhesive

• Construction adhesive, or mastic, that is spread liberally around the collar will adhere the flexible duct to the boot. Be sure to scrape away any residual mastic before spreading new adhesive. Slip the flexible duct onto the collar and press it in place until it holds securely.

Tape

• Wrap the joint where the flex and boot meet with HVAC-grade duct tape. Sealing with tape is not mandatory but provides additional protection against knock-offs. HVAC-grade tape costs more but holds better than standard duct tape.