A picture of a hand being placed up to an open air vent in a house with gaps between the drywall and the air vent, letting hot attic hot air leaking into the house.

Air duct sealing is the process of eliminating any cracks, loose connections, or holes in the air ducts in your home. By doing this you can save money on your utility and energy bills as well as increase the efficiency within your home.

Today, we’re going to show you how.

Air ducts are roadways for air to get from your mechanicals such as your heater or air conditioner to the rest of your home. The system as a whole is usually known as HVAC (Heating, Ventilation, and Air Conditioning).

Ducts distribute the air throughout the home and are designed to be air-tight to prevent any air leakage. This, however, does not always work as planned.

Sometimes the connections between air ducts become loose, or the ducts themselves develop cracks or holes. In these cases, air escapes and does not get to its intended destination.

When there are leaks or cracks in air ducts, it makes the mechanicals work harder to get the home to the desired temperature. This uses a lot of extra energy and can make electrical bills rise.

The home may not get to the temperature it is set at, or different floors of the home can be drastically different, depending on the leak’s location.  Sealing air ducts will increase the efficiency of your home and reduce the amount of money you are spending on energy bills.

If you aren’t familiar with air duct sealing, this article has a lot of great information to get you started.

So Does Air Duct Sealing Actually Work?

With proper air duct sealing, you can generally save 10-30% on your HVAC costs per year. Sealing the air ducts with either air duct sealing tape or a paintable sealant product like Mastic prevents conditioned air from escaping, allowing your air conditioner to work more efficiently.

How Are Air Leaks Identified?

Air leaks in the ductwork can be very challenging to identify. Unlike windows or doors, ductwork runs throughout the house – in the attic, basement, walls, and ceilings.

Homes usually have between 30 and 90 feet of ductwork installed in them which makes inspection and identification of air leaks difficult to accomplish.

Two construction workers perform air duct sealing
Professionals know where to look for leaks and what to do when they find one.

Professionals have the means to identify air leaks in air ducts more efficiently than most DIY homeowners. They use foam to seal off the ducts and force air out of the leaks or cracks. This allows them to identify the specific location(s) where air leakage is occurring.

Air Duct Sealing: The Basics

Similar to performing the inspection, having a professional seal your air ducts will likely save you a lot of time and frustration.

Basic air duct sealing can be done as a DIY with aluminum duct tape and a sealing mastic. However, if there are multiple leaks or large air leaks, having a professional install the air duct sealing is likely a more long-term and sustainable option.

In addition to using aluminum duct tape and sealing mastic, insulation can be installed around the ductwork to minimize any heat loss to the air around the duct.

This also acts as an additional barrier to air leakage. (Make sure that you never use regular duct tape to seal air ducts. It can be unsafe and is not sustainable.)

A picture of a hand being placed up to an open air vent in a house with gaps between the drywall and the air vent, letting hot attic hot air leaking into the house.
With our own air sealing project on our first net-zero house renovation, we’re feeling the air gaps between this drywall and the air vents.

There are some specialized air duct products  such as Aeroseal which are designed to seal entire systems and not just a few leakage points. These are liquids that are sprayed into the air ducts and solidify upon coming into contact with a solid material (the air duct itself).

This seals off any and all air leakage points within the system without damaging the mechanicals attached or sealing off the vents. A product like Aeroseal will fill even the smallest leakage points in the hardest-to-reach places, making it very effective.

A man in a dull green shirt holds up an air duct leakage tester and is reading the measurements for the duct system leakage in our first net-zero house.
To be 100% sure, you may want to order a duct leakage test, which usually is part of, or at least is very similar to, a blower door test.

Luckily, a professional can help you determine the severity of your air leakage within your air ducts and identify the best plan of action for sealing them.

If you do not have a lot of experience working with air ducts, hiring a professional can be more efficient and effective in the long term.

Project Cost Estimates for Air Sealing Ductwork

It can be difficult to estimate exactly how much an air duct sealing project may cost because it is very much dependent on the size of the home, the amount of ductwork present, and the severity of the leakage.

DIY Air Sealing Ductwork Cost Estimates

If you want to air seal your ductwork yourself, you can use aluminum duct tape and a sealing mastic to fill the gaps or holes. This is fairly inexpensive, typically less than $50 depending on how much and what brand you purchase.

To take your air sealing to the next level and minimize air leakage even more, you can install ductwork insulation. This is a bit more of an investment, about $250, but will prevent both air leakage and heat transfer within the system.

You can also remove your air vents in the house and use basic caulk to seal around the edges, so attic air won’t leak into the house.

A man running his finger around the edge of an open air duct vent in our net-zero house renovation. The purpose is to seal the air gaps between the vent and the drywall, preventing unwanted attic air from leaking into the house.
It doesn’t have to look pretty! Just make sure the gaps are sealed between your vents and your drywall so that attic air won’t leak into the house.

The downside to air sealing your own ductwork is there can be places that are nearly impossible to reach within the air duct system.

Additionally, there can be small leaks or cracks that are hard to identify. This could minimize some of your hard work if you continue to have air leakage within the system.

Professional Air Duct Sealing Costs

Depending on the type and severity of the air leakage in your ducts, a professional may choose to use the aluminum duct tape/mastic/insulation method to repair your air ducts. Most HVAC professionals, however, use a product such as Aeroseal to do air duct sealing.

This is significantly more expensive but is much more effective than its DIY counterpart. Professional air duct sealing usually costs between $1,500 and $4,000. Luckily, this upfront cost will usually pay for itself very quickly in the form of energy savings.

It is also a much more long-term and sustainable solution for air duct sealing and ensures that all air leakage points get sealed, even in the toughest locations.

Our Own Net-Zero Home Renovation Air Sealing Costs

This actually wasn’t a bad project at all. We went through and unscrewed all the air vents in the house, and just used basic caulk to seal around the edges between the drywall and the vent housing/metal. You’ll also want to inspect


Brown dog napping under a table in a comfortable house
Money in your pocket and a comfortable home. Win, win! Photo by Tim Foster on Unsplash

Air duct sealing is one surefire way to decrease your monthly energy bill and increase your home’s energy efficiency.

Whether you choose to perform the inspection and air sealing yourself or hire a professional, the energy savings will far outweigh the upfront costs of the project.

The DIY options are cheaper to do and can be done by you; however, leakage points may be missed in hard-to-reach places.

On the other hand, a professional air duct sealing contractor can have a large upfront cost but will guarantee all air leakage points within the system are eliminated long-term.

No matter which option you choose, you are bettering your home and keeping money in your pocket.

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