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

You can seal a leaking air duct by cleaning the joint and applying mastic sealant or metal tape, then insulating the duct to lock in the gain and boost HVAC efficiency. In many homes, about 20 percent of the air that moves through the duct system is lost due to leaks, holes, and poorly connected ducts, so joints and seams are the usual culprits. Focus on accessible runs in attics, crawlspaces, unfinished basements, and garages; a quick flashlight-and-fan test often flags leaks before you touch a tool. Technicians working throughout the Hamburg area can also pressure-test ducts and repair hidden failures that DIY methods miss. A small brush for mastic reaches into seams better than a gloved finger, which helps the seal last through seasonal expansion.

If you want a simple DIY path:

• Find: Run the blower, feel for drafts, and look for gray dust streaks around joints.
• Seal: Clean surfaces; apply mastic or metal tape; never use duct tape, as it is not long-lasting.
• Insulate: Wrap sealed sections to reduce heat gain or loss.

If you smell exhaust, see soot, or suspect carbon monoxide, shut the system off and call a professional immediately. <br/> Updated: 2026-03-25 <br/> Need help in Hamburg, NY? Call (716) 216-5332 or book online.