How To Fix It

Does Ductwork Need To Be Sealed?

The ductwork in a home or commercial building is intended to help control the airflow throughout the facility. Ductwork is created with sheet metal and has many different types of joints that are used for different purposes – each joint type affects the overall airflow through ducts. 

Ductwork needs to be sealed to improve indoor air quality and prevent contaminants from entering the ventilation system. Additionally, sealed ductwork will decrease energy loss by increasing the efficiency of forced-air systems. 

Sealing duct seams can prevent air leakage but will not provide a “one hundred percent” seal. In this article, I will discuss the different types of joints in a typical duct system, their function, and how they should be sealed. 

Why You Should Seal Your Ductwork?

Ductwork is made from sheet metal as well as different types of joints that are used to create the airflow path through the ductwork – each type of joint has a specific purpose and affects the overall airflow. 

Ducts can lose up to 30% of air due to poor construction. Sealing seams and joints on existing ductwork may increase energy efficiency and indoor air quality by reducing contaminants entering into ventilation systems. 

As an added benefit, sealing your ductwork could save you money every month on heating and cooling bills. 

Read: Ductwork Insulation: Everything You Need To Know

How To Seal Your Ductwork?

There are three main types of products that can be used to seal your ductwork: 

  • Mastic sealant 
  • Aeroseal duct sealant 
  • Metal-backed tapes 

If you are looking to ensure a better seal for your duct, go with a professionally installed method. These three methods are the best way to seal up ducts.

To seal your ductwork yourself, you can use mastic sealant combined with metal-backed tapes or aeroseal to ensure the job is done right.

A professional method for sealing ducts is to use acoustical sealant combined with metal-backed tape in order to create a double barrier around the seams of the duct. 

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These products serve as barriers themselves and allow for easier future HVAC system maintenance. 

Use Mastic Sealant

Mastic sealant is a putty-like material that fills the area around a duct, creating a more solid seal. To use mastic sealant, clean the area around where you are applying it with a damp rag, then simply press it into place. 

These systems can fill gaps as wide as 1/2″ (1.27 cm) and come with an applicator that allows you to precisely seal those hard-to-reach spots without having to break out gallons of mastic material. It also comes pre-mixed, so there’s no mixing up multiple batches. 

Read: How Hard Is To Replace Ductwork?

Use an Aeroseal Duct Sealing System

The Aeroseal system uses dry dust material to seal any leaks in your ductwork. While this is not an instant solution like mastic can be, it can work for places that are hard to get to or reach.

The Aeroseal method is done by professionals, so you will need to consult an HVAC service company if you are interested in this method. 

A professional will ensure that the internal components of your furnace are also shut off when using the Aeroseal duct sealing technique to ensure they are not damaged by the sealant flowing through the ductwork.

Aeroseal technology can detect all of the leaks and flaws where air escapes owing to pressure application. 

While there is no perfect solution for sealing ductwork, there are some great options that can help get rid of the problems with your ducts while not causing too much hassle for you. 

These systems usually come with long warranties (upwards of 20 years) and are generally low-maintenance.

The mastic system may be your best option if you do not have the means for professional installation or if your ducts run through the attic only. 

Read: How Hot Can Ductwork Get?

Use a Metal-Backed Tape

This option provides you with long-term sealing power. It works by winding round and round until it covers all areas where air could escape through your ducts.

Unwind just enough tape for each section of your ducts, then use a small piece of sandpaper to remove any burrs from the metal edges. 

Metal-backed tape can be a DIY project but must be installed correctly to function properly. Be sure you are using the right tools and have the proper knowledge before attempting to install it yourself. 

Although duct tape might not be a common name in sealing supplies, it is an acceptable option if you are looking for something temporary.

Like foil-backed tape, it works by covering all areas where air could escape through your vents. 

Some people choose to use this type of tape because they are unaware that there are better options available.

Keep in mind that duct tape will stretch when exposed to heat, so any slack will open up new spots where air can escape. This product should only be used in an emergency or while installing a permanent solution. 

Read: Should Ductwork Be Replaced After 20 Years?

How Do I Know if My HVAC Ducts Are Leaking?

Knowing if your ductwork is leaking can be difficult. If you are unsure, the best thing to do is contact a professional HVAC company or technician.

They will be able to inspect your system, ensure that all parts of the unit are working properly, and also ensure that your ducts aren’t leaking. 

To know if your HVAC ducts are leaking, turn on your HVAC system and go back to the locations where ductwork is visible. Look at the connections between each section of ductwork, placing your hand over the metal. If you feel air, the connection is loose, and there is an air leak. 

The best way to identify if your HVAC ducts are leaking air is with an infrared camera. These devices can detect where and how much air is escaping and will map out the areas that need immediate attention. A specialist can then follow up by sealing any leaks that were detected with mastic sealant. 

Read: Should Ductwork Be Insulated?

The Cost of Professionally Sealing Your Ductwork

Repairing problems after they occur will help retain the value of your home and ensure that costs associated with energy bills don’t get out of hand. 

HVAC contractors use an insulation blower door test to assess if there are any significant leaks present in a home’s ductwork. This is similar to a pressure test, where a vacuum is created on one side of a wall while air pushes from the other side to try and force its way through any cracks or openings found within the construction. 

For most homes, it can cost up to $1,500- $4,000. These tests often require two people and take between 30 minutes and two hours, depending on the size of your home and how leaky your ducts are determined to be. 

DIY duct sealing costs are much cheaper, but keep in mind that you may forfeit any warranty that may be associated with the system. The cost of DIY duct sealing can range from $20 to $200 depending on how many areas need treatment and the size of the area being sealed. 

Some ducts have more than one opening, so you can expect higher costs for this service.

DIY sealing is a great way to save money if you are willing to take the time and energy needed to ensure a proper seal. Remember that the most important thing in either DIY or professional duct sealing is to find all of the leaks in your system.

There’s no point in getting it done twice, so make sure to check over every bit of it after it has been serviced before using your HVAC again. 


Ductwork should be sealed properly, but there is a significant difference in the quality of service between a DIY seal and a professional seal. The best way to make sure your ductwork is sealed properly is to do it yourself if you have the time and energy. 

Alternatively, check reviews online for local HVAC companies that can offer duct sealing services. As with any contract or investment, it’s important to do some research before spending money on this procedure, so you know exactly what kind of service you are getting.