Duct Caps

Duct caps close off the end of an HVAC duct run, protecting airflow, efficiency, and cleanliness across residential and commercial systems. Whether you are pressure-testing new ductwork, isolating a future branch, or retiring an old takeoff, the right cap prevents leaks, keeps debris and pests out, and maintains target static pressure.

Options include round duct caps for spiral and snap-lock pipe, rectangular end caps for S-and-drive duct, and flexible duct end caps for temporary sealing. Common materials are galvanized steel, aluminum, and high‑temperature plastics, with choices from light 30–28 gauge up to 26–24 gauge for higher pressure. Insulated duct caps reduce heat gain or loss at the termination and help control condensation.

Select by matching the nominal size and connection type: crimped or uncrimped round, slip or drive cleat rectangular, and beaded spiral fittings that accept draw-band clamps. Check pressure class, temperature rating, and any required listings (such as UL standards used in HVAC). In coastal or humid environments, corrosion‑resistant finishes extend service life.

Installation is straightforward: cut square, deburr, seat the cap fully, fasten with three equally spaced sheet‑metal screws on round duct or appropriate cleats on rectangular duct, then seal with water‑based mastic or UL‑listed foil tape. For flex, clamp the inner core first, seal, then pull the jacket and insulation over the cap and tape or strap. Label capped branches for future use.

Routine inspection helps catch dried tape or loose fasteners. Properly sealed caps improve comfort, reduce blower workload, and lower energy costs by eliminating wasted airflow. They also protect indoor air quality during construction by keeping dust out of clean duct.

Find sizes from 4 in. to 20+ in., along with accessories like mastic, foil tape, draw-band clamps, and insulation wraps to complete a code‑ready, airtight install. Shop durable, tested duct caps for reliability.