A dented air duct with holes above the words "Checking Air Ducts for Leaks"

Your home’s HVAC system consists of many parts, including an indoor unit, an outdoor unit, vents, and a system of ductwork. When you have signs of your A/C and heating system not working properly, the issue could be located in any one of these parts. Unless your unit has completely stopped providing your home with hot or cold air, one of the best places to start looking for the issue is in your air ducts.

Signs that your Air Ducts May be Leaking

There are many signs of issues with your ductwork. Common problems caused by air duct leaks include:

High Utility Bills

Unless you’ve recently used excess energy for a party or other occasion, a spike in your utility costs is likely due to an issue with your HVAC system. When there are air duct leaks, it means that your system is spouting cooled or heated air into your attic, basement, or other unwanted location, and therefore requires more energy to properly cool your home.

A Dusty Home

When’s the last time you dusted your attic or basement? The answer is likely “never.” When your ductwork leaks, it’s likely going to pull some of the built-up dust in these spaces and spew them into your home. This will lead to increased allergy attacks and a greater amount of dust around your home.

Uneven Heating and Cooling

Is one room cold while another one on the same floor is hot? Unless there is a constant flow of outside air into one of the rooms or one gets a high amount of direct sunshine, the issue is likely due to an air duct leak.

How to Locate Leaks in your Ductwork

There are a few steps you can take to locate leaks in your ductwork.

1. Look for Obvious Tears

The first step is obviously to look for visible tears in your air ducts. Mark these spots with a grease pencil so that you can come back and fix them once you’ve finished checking your whole system for leaks.

2. Turn your HVAC System on Full Blast

If your HVAC system isn’t blowing air when you’re checking your ductwork, you won’t be able to locate less obvious leaks. The greater the amount of air that’s flowing through, the easier it will be to find air duct leaks.

3. Check the Duct Joints

The spots where two air ducts connect are common places for leaks to occur. If you place your hand near these joints and you feel air coming out, you know that there’s a leak. You can also try running your hand under other parts of your ductwork to feel for larger leaks. Mark any leaks you find with a grease pencil.

4. Look for Duct Tape

Duct tape is not actually meant to seal most ducts – at least not as a permanent fix. If someone previously tried to seal up a leak using duct tape, you’ll want to remove this so that you can seal up the leak properly.

5. Light a Smoke Pencil or Incense

Anything that gives off visible smoke will be a useful tool when trying to find air duct leaks. Slowly run the incense or smoke pencil underneath the ductwork. The flame and smoke will likely be more sensitive to smaller leaks than your hand is. If you see the smoke twirl in an unusual pattern, you know that the smoke is being blown or sucked up by the air duct. It’s especially important to mark these more subtle leaks so that you can seal them up later.

6. Seal Up the Leaks You’ve Found Thus Far

There’s one more step that you can take to locate remaining leaks, but you need to seal up the leaks you’ve already found first. There are two methods you can use to accomplish this. The first is to seal the leak by wrapping the air duct in foil-faced tape. The other method is to apply mastic to the leak.

7. Use a Fog Machine

Obviously, not everyone has a fog machine at hand, but there are plenty of places that will rent them out. To use this tool, first you need to seal up all your air vents. Next, place the fog machine by your furnace or blower intake fan. This fog will be very visible as it comes out of your air ducts.

The reason that you need to seal up any other leaks before using the fog machine is that if the fog is flowing out of several holes, your attic or basement will quickly fill up with smoke, making it difficult to locate where the smoke is coming through. Seal up any leaks you find using mastic or foil-faced tape.

These methods will not work in every case. Sometimes, ductwork is located in areas that are difficult to access. Other times, the leaks in your air ducts are so extensive that the best thing to do is get your ductwork replaced. Then again, the problem may be located in another part of your HVAC system instead of or in addition to your ductwork. In any of these cases, you should contact the HVAC experts at Comfort Masters Heating & Air Conditioning. They’ll quickly locate the source of the issue and get to work on fixing it.