Air ducts in a home with metal-baked tape applied to prevent air duct leakage

If you’ve noticed drafts in your home or a more expensive heating or cooling bill, you may want to take a look at your home’s air duct system.

Inefficiencies in the ducting can cause energy loss through gaps and cracks, which in turn raises your utility bills. 

But how do you know if you have leaker air ducts?

What Is Air Duct Leakage?

Air duct leakage can be caused by loose ductwork, gaps, tears in flex, and insufficient attachments.

A few leaks here and there in your ductwork shouldn’t be a problem but where there is one leak, there could be more.

Which ultimately means you’re spending money to heat and cool unused spaces in your home and your HVAC equipment has to work harder to satisfy the thermostat setting.

Air duct leaks can also lead to excess moisture in the house and poor air quality.

What Are the Indicators of An Air Duct Leak? 

High Electricity Bills

If your electric company hasn’t increased your electricity’s kWh rate, and yet your bill has increased, you may have a leaky duct system.

If the leaks are substantial, your HVAC system will run more to keep up. 

It’s important to note that unusually high electric bills might not always be leaking ductwork. There could be something wrong with your furnace or air conditioner. If you don’t find any leaks in your ducts, you should have a tech out to service the unit.

Poorly Distributed Heating and Cooling Throughout Your Home

If you notice certain areas of your home that are cooler or warmer than the rest of the house, you could have an issue with the ductwork.

More Dust and Grit in Your House

Holes in the return section of the duct will draw dirt, dust, pollution, pollen, and other particles into your home through the ductwork.

You may notice that the floors and furniture that immediately surround your vents are grittier than usual, especially when the system is running.

Testing for Air Duct Leaks

Before paying to bring in a professional, you may want to investigate ductwork to confirm that you have a leak. 

How to Test for Air Duct Leaks on Your Own

Go into the basement or utility room and take a look at the ductwork coming off the furnace. Look for visible holes, gaps, bent or kinked ducts, and loose connections in the ductwork.

If the furnace is running, you should be able to feel air leaking out. If you’re not sure, grab a lighter and hold the flame up to the spot you think is leaking. If it flickers, you have a leak.

How a Certified Tester Checks for Air Duct Leaks 

Professionals will use a blower duct test to quickly and efficiently locate any holes in your system. This is very similar to a standard airtightness test. 

A professional uses a blower duct test to inspect home air duct leakage

Similar to a blower door test, blower duct tests take twenty to thirty minutes to prepare for and another twenty to twenty-five minutes to complete. These tests are also affordable for most—Aeroseal offers the service for $99. 

The professional will place temporary seals over all of the grills and registers in your home. With those seals in place, they can determine how significant the leaks or holes are in your ductwork system. 


To test airtightness of doors or air duct leakage, BPI or RESNET-certified professionals most commonly use RetroTec DucTester or Retrotec Blower Door systems, and Minneapolis Duct Blaster or Blower Door systems. 

RetroTec DucTester Systems

RetroTec’s most popular DucTester system is the Model 300x DucTester. This system is used by energy auditors, HVAC contractors, building contractors, building remodelers, and home inspectors. This lightweight system features a DM32 wifi gauge, a roll of Grill Mask to seal off registers, and three flow ranges (open, 47, 74, and 102). 

You may choose between 120V and 240V and one or both of these software solutions: FanTestic Lite and FanTestic Pro (Residential Duct Testing US at 25p).

Though intended for professional use only, training and reporting software is included with the system, making it accessible for all. And just in case you’re unsure of your operational abilities, five-year extended warranties are also available. 

RetroTec Blower Door Systems

While Retrotec offers several models in various sizes, the Retrotec 5100 Blower Door System is one of their most popular products. This system is suitable for residential or small commercial use.  

It offers a variety of frame sizes for different door sizes, 120V or 240V, and offers two software solutions: FanTestic Lite and ASTM E-799-10 (it offers customizable reports). 

Blower door fan cases are available, as well as five-year extended warranties for the system. 

Training and reporting software is included with the system, making it accessible for all. 

Minneapolis Duct Blaster

The Minneapolis Duct Blaster is the industry standard for testing the performance of forced air distribution systems for BPI or RESNET-certified professionals.

A Minneapolis blower duct blaster system is used to test air duct leakage in a home
Courtesy of Blower Door Tester

It connects directly to your home’s duct system, usually at a central return. The remaining registers and grilles are then taped off, to accurately gauge air duct leakage through pressurizing or depressurizing the duct system and getting an exact measure of the duct pressure and fan flow.

Minneapolis Blower Doors

The Minneapolis Blower Door System is one of the best-known blower door systems because of its thoughtful design and well-supported airtightness testing system. 

Types of Ductwork

The two main types of ductwork you are likely to see in your basement are sheet metal and flex

Sheet metal will make up the main trunk of both the return air and the supply. There will be offshoots from these two trunks made of rigid pipe and flexible pipe. 

The sheet metal ducts are assembled in sections and held together by clips and drives. Check the seams and the corners for potential leaks.

Now you can go back and check the offshoots. These sections of pipe go to the vents in your floors. Here, you want to check that the connections are secure and there are no gaps.

Tools Needed for Repairs

Once you’ve determined that air duct leakage is occurring and have pinpointed all the leaks you can find, you can go in and seal them.

Below are some of the tools you will need to fix your issues during the inspection. They are all basic enough to be found at your local home improvement center.  If home repairs aren’t your thing, contact an HVAC company for service.

  • Flashlight
  • Screwdriver
  • Rags
  • HVAC aluminum foil tape (DC 181)
  • Mastic sealant
  • Paintbrush

Depending on where the leaks are, you can seal them with the foil tape, or use mastic sealant. For mastic sealant, you simply use a small paintbrush to apply it to the seams of the leaking ductwork. It’s a pretty simple fix and easily something you can do yourself.

But be prepared, mastic sealant can get a little messy.

What Causes Ductwork Damage? 

Poor Maintenance 

Having your air ducts professionally cleaned and inspected every three to five years can help keep your system running at peak performance.


Ductwork can last anywhere from 20 to 25 years, depending on maintenance and repairs. Taking preventative action early can help monitor necessary repairs and replacements.

Pests or Animals

No matter how vigilant a homeowner is, these critters can still make their way into air ducts to cause extensive damage. Watch for signs and listen for the sounds of possible pests or animals in the air ducts. Take action immediately.

Mold or Condensation

Condensation can lead to rust on the ductwork and eventually result in poor air quality, leading to multiple health issues for those living there. If the ductwork has enough rust on it, it can detach from the main trunk.

Impact Damage

Air ducts located in areas that have high traffic stand the risk of being damaged by accident and can lead to big repairs.

Final Thoughts

Leaking ductwork can be a financial drain but it’s a problem you should be able to take care of yourself in a single afternoon. 

Unless there is major damage to the ductwork that needs a professional to repair and reinstall, you can save a bit of money sealing the leaks yourself with DC 181 foil tape and mastic sealant.

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