Duct Accessories

For flex duct connections, UL-listed aluminum foil tape is the standard — it creates an airtight seal and is fast to apply. Our aluminum foil tape is UL 181A-P and UL 181B-FX listed, rated from -30°C to +150°C. Mastic (a brush-on sealant) is better for rigid duct seams and irregular joints because it fills gaps. Many HVAC professionals use both — mastic on the joint plus foil tape over the top for belt-and-suspenders sealing. Never use standard cloth "duct tape" on HVAC ducts, as it fails within months. See our duct sealing guide for best practices.

Per IRC/IMC code, flex duct must be supported every 5 feet maximum, with no more than ½" sag per foot between supports. Our duct hangers and straps are 1" wide (code minimum) to prevent pinching the duct. At connection points, support the duct within 12 inches of the fitting. Sagging duct creates turbulence and can reduce airflow by 15–30%. Always pull flex duct taut before securing it. For horizontal runs in attics, use saddle-type hangers rather than wire, and never let the duct rest directly on ceiling joists. More installation tips in our flex duct installation guide.

Duct connectors must match the inner diameter of your flex duct. Our flex duct connectors are available from 4" to 20" and use a worm-gear clamp (draw band) mechanism for a secure, airtight fit. Slide the flex duct core over the connector collar, secure with the clamp, then seal with foil tape. Make sure to pull back the outer jacket and insulation (if any) before connecting, then tape everything down over the joint. For a step-by-step walkthrough, see our duct connector guide.

Flexible connectors (also called flex joints or vibration isolators) are short sections of fire-rated fabric that connect an air handling unit or furnace to the rigid ductwork. Their primary purpose is vibration isolation — they prevent motor and fan vibration from transmitting through the duct system, which reduces noise and prevents fatigue cracks in rigid duct seams. Our flexible connectors feature fire-rated fabric construction and are available in flanged or slip-on configurations. They are required by most mechanical codes at every equipment connection. See our duct fittings guide for installation details.

Yes — our duct connectors, foil tape, and hangers work with both insulated and non-insulated flex duct. The key difference is installation technique: with insulated duct, you must pull back the outer vapor barrier jacket and insulation layer, connect the inner core to the connector, seal with foil tape, then fold the insulation and jacket back over the joint and tape again. This double-seal method prevents both air leaks and thermal bridging. Use the same 5-foot hanger spacing for insulated duct, but use wider strap supports to avoid compressing the insulation. Our duct insulation guide covers the full installation process.