How Can I Seal a Leaking Air Duct to Improve HVAC Efficiency?

To seal a leaking air duct, apply mastic sealant or UL 181 foil HVAC tape to cleaned, dry joints and seams you can access safely. Most leaks start at loose connections around boots, plenums, and takeoffs where original tape or sealant failed with age or vibration. Small, reachable gaps are good DIY targets; widespread or hidden leaks usually need pro testing and sealing to restore efficiency. Technicians serving the Roanoke–Salem area can pressure-test ducts and seal them with advanced diagnostic tools for a tighter system.

Try these focused steps on accessible metal or rigid-duct sections:

• Turn off HVAC, remove old tape, clean surfaces, and dry.
• Brush on mastic; embed mesh for gaps larger than a pencil width.
• Use only UL 181 foil tape on straight seams; avoid cloth “duct tape.”
• Seal the air handler plenum edges; leave service panels removable.

If airflow drops or rooms stay uneven after sealing, schedule a professional duct inspection and pressure test.

Updated: 2026-02-25

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