Seal leaky ducts

Why? Ducts distribute air from your heating, cooling and ventilation systems throughout your home. When ducts have leaks, they can lose up to 20% of heated or cooled air. Just like opening the window while the heat or air conditioning is on, leaving your ducts in poor repair wastes energy and money.


  • Check for obvious holes throughout the duct system. Focus your repairs on ducts you can easily access, such as those in attics, basements, crawlspaces and garages.
  • Seal duct joints and any leaks. Use aluminum foil duct tape or  mastic, a flexible sealant, to seal leaks and cracks, since it lasts longer than regular duct tape. For holes and gaps up to half an inch across, reinforce the mastic seal with fiberglass mesh tape. Larger gaps may need to be repaired with rigid material.
  • Insulate accessible ducts. This will help prevent heat loss into cold areas. Visit the ENERGY STAR® website to learn more about insulation and draft-proofing.

Good to know: Homeowners can choose from many types of mastic. Be sure to select a sealant that will work well in your home.

Professional option: Hire a reputable contractor to seal and insulate ducts that are hard to reach or especially leaky. A contractor should also inspect the entire system to ensure it is functioning optimally and conduct other repairs, like fixing damaged ducts and sealing registers.

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Save up to $300 per year

Up-front costs: Varies. A roll of aluminum foil duct tape costs about $13.