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 heat/cool air loss, which in turn raises your utility costs. 

If you’re wondering how to test for air duct leakage, you’ve come to the right place. This article will explain how to test for leaks, describe the different types of ductwork, and help you determine which tools to use. 

What Is Air Duct Leakage?

Air duct leakage can be anything from a loose duct line to a tear or hole in the ducts, depending on the type of ductwork you have in your home.  

Testing for air duct leakage is essential for energy efficiency and to prevent unseen damage to the home’s structural integrity. Air duct leaks can lead to excess moisture in the house, poor air quality, energy loss, and extensive wear on your heating and cooling units. 

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 leak. 

Leaky ducts will make your HVAC system work much more challenging to maintain temperature, much of which is lost and wasted with a leak. 

Poorly Distributed Heating and Cooling Throughout Your Home

If you notice that one room is consistently a different temperature than the rest of your home, you may have a leak.

A leak in the ductwork will let too much air escape from the vents, which causes one or more of the rooms in your home to be skipped over by the heating, ventilation, and air conditioning (HVAC). If you have to run your HVAC machine significantly more than usual to reach your desired temperature, the leak may occur on the main branch before the air is distributed to any individual room. 

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. This is a good indicator of a leak or hole. 

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

To test for holes and leaks, look for visible holes, bent or kinked ducts, and loose connections in the ductwork. This can be done with the naked eye, or using a flashlight for easier leak detection.

The test further, turn on your HVAC system. Then grab a candle or incense stick and walk along the ducts. Place your hand on the metal and feel for temperature fluctuations. Carefully check the connections, and feel for air hitting your body or hands. If the flame wavers or flickers, inspect that section for flaws. 

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. 

Equipment

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. 

The Three Types of Ductwork

Flexible Ductwork

This type of ductwork is typically tube-shaped, made of a wire coil covered with bendable, durable plastic, and surrounded by insulation.

Rigid Ductwork

Rigid ductwork comes in various materials and sizes, is insulated, and is more popular due to its durability and reliability. Businesses usually rely on this form. 

Semi-Rigid Ductwork

Semi-Rigid ductwork offers installers more versatility and optimal performance but has a high crushability rating.

Tools Needed for Repairs

Once you’ve determined that air duct leakage is occurring, have pinpointed the exact location of the leak, and whether your home has flexible, rigid, or semi-rigid, you’re ready to repair. 

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 a BPI or RESNET-certified professional for service. 

  • Flashlight
  • Screwdriver
  • Rags
  • HVAC aluminum foil tape (not duct tape)
  • Mastic sealant

If you find that a large portion of ductwork needs to be replaced, don’t panic. Most repairs simply require new sealant or tape, but if you find more significant gaps or holes in the ductwork, you may need to detach, repair, reattach and seal the ducts. You can easily make these repairs while energy efficiency is preserved.  

These repairs may seem tedious, but they will definitely pay off in the long run on energy costs and the carbon footprint that your home is making.

Now that repairs have been made and your heating/cooling system is back operating at peak performance, let’s review what damaged your duct system in the first place.

What Causes Ductwork Damage? 

Poor Maintenance 

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

Age

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.

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. If your basement has moisture issues, it can cause your ducts to rust.

Conclusion

The maze of air duct lines that flow in and out of buildings is a silent reminder that many aspects of maintaining a home or commercial building are often taken for granted. 

As stewards of this planet, our goal is to leave as small of an impact on our environment as we can. A simple leak in an air duct is small yet significant and worth the effort to repair.  

Now that you have the knowledge and tools to inspect for air duct leaks, you can feel confident you are taking the correct steps to maintain your home or building and doing your part for the environment.

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