6 Signs Your Air Ducts Are Leaking Air

air ducts being installed

Comfy, cozy, cool — that’s what we expect our heating, ventilation system, and air conditioning unit (HVAC) to deliver. One way to throw that trifecta off-balance? Air duct leaks. What are some signs your air ducts are leaking air? To start, you’ll notice higher utility bills, excessive amounts of dust, and uneven heating and cooling of living spaces. 

But First, What Are Air Ducts?

Composed of a series of tubes, an air duct system extracts, contains, filters, and heats or cools air in your home. With the aid of a blower, that air is then delivered from the ducts through air vents in each of your living spaces. 

Located inside walls, ceilings, and/or flooring, this aspect of your HVAC system is typically made of:

  • sheet metal
  • fiberglass
  • steel wrapped in flexible plastic

6 Signs Your Air Ducts Are Leaking Air

1. You Notice Suddenly Higher Utility Bills

Leaky ducts cause heated and air conditioned air to escape into areas of your home that don’t really need it — non-living spaces like your attic, crawl space, and unfinished basement. When this happens, your heating and cooling system will be forced to work harder and run longer to reach the desired temperature in the rest of your home. This excess energy spend will, in turn, lead to more expensive energy bills.

2. Pests Have Damaged Your Ductwork

Another common sign of leaky ductwork is evidence of a pest infestation. All sorts of vermin (like snakes, rats, mice, and roaches) can get access to your ductwork in the same way air can leak out of your ductwork — through holes, rips, or tears. These pests can also cause air leaks on their own by gnawing holes right through your duct sealant and insulation.

Chew marks, shed skin, eggs, droppings, animal noises, and a musty stench are all unmistakable symptoms of a pest issue.

3. You Notice a Greater Amount of Dust

Normally, dust stays stuck on air duct walls, never really getting through the duct’s air filter and into your home. A significant amount of dust buildup, however, can impede airflow, jeopardize air filters, and cause allergic responses. This isn’t your average, run-of-the-mill dust level that accumulates from week to week; this is dust that seems to persist no matter how often you polish your furniture, vacuum your carpets, or wash other household fabrics.

How does this happen? No longer able to filter such excessive amounts of dust, your heating and AC units will continuously draw in dust from less used areas of your home (e.g. your attic), distributing it, along with the heated or cooled air, throughout your house.

4. There’s an Overall Decrease in Indoor Air Quality

Besides a marked increase in the amount of dust in your home, air duct leakage can contribute to dirty air in other ways, too. Take, for instance, hot, cold, and/or polluted outside air; through duct leaks, this air and its contaminants can be sucked in and blown out to various parts of your home.

What’s more, inside air originating in places like your attic, unfinished basement, and/or crawl space may contain contaminants, including combustible materials given off by your furnace, fireplace, or water heater. This air is then sent out through air vents all over your home.

5. Your HVAC System Often Needs Repair

The average lifespan of an HVAC system is about 20 years, depending on things like system type, location/climate, size, insulation, and whether or not you keep up with regular maintenance. If your central air and heating system is not that old, and you find yourself constantly needing an HVAC technician to repair it, this could be another sign of leaky HVAC ducts.

6. Living Spaces Experience Uneven Heating and Cooling

Your air conditioning system is functioning properly when all living spaces are uniformly cooled; the same goes for your heating system in fall and winter. But, if you notice some rooms are still too hot or too cold, the culprit could be leaky air ducts. Air leaks can prevent cold air or warm air from reaching certain areas of the house, resulting in uneven heating and cooling.

FAQ About Air Duct Leakage

What types of duct leaks are there?

There are three main types of air duct leaks:

  • return duct leaks
  • supply duct leaks
  • equipment leaks

A return duct leak means unconditioned (or unheated) air is extracted from places like your attic, crawl space, or garage and distributed throughout the house. This increases the energy output from your HVAC, as it is having to cool or heat air from scratch, rather than recycling already heated or cooled air.

A supply duct leak is when airflow from the air conditioner or heat pump/furnace to other areas of the home decreases. This can contribute to uneven heating and cooling in your living spaces.

An equipment leak happens when components of your HVAC system have faulty seals, allowing air to escape and airflow to decrease.

Can I use duct tape to seal air leaks?

It’s not recommended that you seal air leaks with duct tape (regardless of what the name implies), as the tape isn’t meant to stand up to extreme heat or cold like what is produced from your HVAC system. Instead, call an HVAC technician to attend to the leaks properly.

How can you find the source of an air duct leak?

To find the source a potential duct leak on your own, try the following:

  • Do a visual check for any tears in the ducts or gaps in duct joints. Leaks commonly happen at these joints, so make sure the sealant is intact.
  • Watch out for any duct tape. Previous owners may have noticed leaks in the ductwork but rather than repair them, they may have used duct tape as a temporary fix. The tape will make it easy to identify the location of these leaks.
  • Turn your HVAC on full blast. Raising or lowering your thermostat several degrees (depending on the season), so it kicks on will help you quickly identify any areas of uneven heating or cooling. Then, you’ll know there’s an air leak somewhere nearby.
  • Perform a flame test. Using a lighted candle, smoke pencil, or incense, go from room to room, taking note of any times where the smoke from your lighted item is drawn into an air duct. This method only works for small air leaks.

When to Hire a Professional

It’s possible for homeowners to DIY duct sealing of some air leaks, like those found in an unfinished basement or attic. When it comes to repairing leaks in harder-to-reach areas, though, it’s best to get help from an HVAC professional near you. To accurately identify and fix any issues, a skilled HVAC technician will thoroughly evaluate your air ducts and reseal them as necessary, restoring you with a system that operates with much more energy efficiency.

Main Photo Credit: welcomia / Canva Pro / License

Andréa Butler

Andréa Butler is a writer and editor. And while she hasn't been blessed with DIY skills herself, she is adept at writing and enjoys sharing home improvement tips and pool care guides for the true DIYers out there.