Sealing Your HVAC Ducts: How to Do It and Why It’s Important

When it comes to your HVAC system, it’s all about energy efficiency. How do you get the most out of your system and still have manageable energy bills? What can you do if your bills are too high? How can you increase your unit’s efficiency without purchasing a new unit altogether?

If you’ve tried changing your air filters, installing a programmable thermostat, and other things to lower your energy bills with no luck, your ducts could be the problem. Duct leakage can affect your family’s comfort and your bottom line, and in many cases you can fix the problem on your own.

Heating Ducts

What is duct leakage?

Duct leakage occurs when the conditioned air in a home escapes your duct system through holes, loosely connected ducts, or improperly sealed duct connections. In fact, leaky ducts can result in the loss of 20 to 30 percent of the air that runs through your HVAC system, according to ENERGY STAR®. Duct leakage does not just lower the efficiency of your home’s HVAC system, but it can also release dust and debris from areas surrounding your ducts into your air and increase monthly energy bills.

How do I know if I have leaky ducts?

Duct leaks can be something of a “quiet killer” when it comes to HVAC efficiency, but here are some easy, at-home ways to tell if your ductwork is costing you money:

  • Your HVAC system is running, but some rooms are warmer/cooler than others
  • Your energy bills are above-average
  • Some of your rooms become dusty when you turn on your HVAC unit
  • You see peeling sealant, metal tape, or duct tape where holes may have been sealed at an earlier time
  • You have visibly crushed, tangled, or kinked ductwork throughout your home

All of these signs point to costly duct leakage problems that may be decreasing the efficiency of your HVAC system.

How do I find where my ducts are leaking?

The first step to stopping leaky ducts is to locate the source. The best place to start is with any exposed ductwork you can see. If you have removable tile ceilings (usually found in finished basements), remove the tiles and look for ductwork to inspect. Look for poor connections at joints, holes caused by wear and tear, and loose, crushed, or tangled ductwork to find the most likely culprits.

If you don’t find any obvious signs of leakage, use the smoke test to locate problem areas. Turn your unit to its fan setting and light a stick of incense (or a candle). Pass the smoke from the incense over the exposed ducts in your home, starting with the places where your ducts connect to the main unit and the areas where two ducts are joined. If the smoke is blown away from the joint or pulled into it, you are experiencing duct leakage.

How do I fix the leaking ducts?

Once you locate where your ducts are leaking, there are some simple solutions for fixing the problem.

  • Seal your joints. Seal any holes, loose connections, or leaky joints with duct mastic sealant or metal duct tape. Unlike traditional, cloth-backed, rubber duct tape, these sealants are long-lasting and provide the sealing strength you will need to stop leakages long-term.
  • Inspect your registers and vents. Are they well-connected? If not, tighten your wall vents and seal any gaps between the duct system and register connections to ensure you are not losing valuable air. Creating tight connections where your system delivers air to your rooms will help you avoid duct leakage and keep your system running efficiently.
  • Insulate your ductwork. Wherever possible make sure your ductwork is insulated, especially if it’s in unconditioned areas like an attic or garage. Insulating your ductwork will reduce opportunities for air to escape your system and provide better HVAC system efficiency, saving you hundreds of dollars over the life of your system.

When do I need an HVAC pro?

If you follow these tips and your energy bills are still higher than average, or if you just don’t feel comfortable crawling through your house looking at your ductwork, use the “Find A Contractor” link on to have our team connect you with a trusted, licensed local HVAC professional from our contractor network that is focused providing you the best customer experience possible.