How to Inspect and Seal Air Duct Leaks

What Is Aeroseal Duct Sealing?

I know I said there were two ways to seal duct, but the key words there were "easiest" and "your own."

Aeroseal is a very nice system developed to seal ducts of all kinds, but this is not a process that you as a homeowner can do yourself. It is typically far more expensive than what most are willing to spend.

That said, it may be the only answer for those who have underground ducts or ducts that they cannot access to significantly seal by hand. It is also becoming more and more popular in new home construction, as the cost is built into the purchase price and not coming directly out of your pocket all at once. Check out this video to see what Aeroseal is all about and how they do it.

Note: Aeroseal is a brand name and there are other companies that use the same type of technology. I am not recommending a brand or company here, only the technology.

Benefits of Air Duct Sealing

You may have wondered if it is important to seal your ducts. The answer is yes. A duct system that is properly sealed is essential because of the following reasons: 

It Provides Better Cooling and Warmth

Duct leaks obstruct airflow, meaning the right amount of air will not reach your vents. To ensure that heating and cooling are improved, proper duct sealing is recommended for overall comfort. 

Prevent Wear and Tear

Like every other electronic system, HVAC units wear out over time, reducing efficiency and necessitating maintenance to keep the unit running at peak performance.

When ducts leak, the HVAC unit is forced to work harder. As a result, they run for a longer time and consume more energy. By sealing the ducts, you reduce the stress placed on the HVAC unit.

Ensures Safety

It is usual for appliances in our homes, like heaters, furnaces, and dryers, to emit combustion byproducts such as carbon monoxide through the duct system.

Backdraft can occur when your ducts leak, and these harmful gases are reintroduced indoors rather than outdoors. Because breathing in these gases can cause health problems, sealing must reduce the risk.


To Seal Ductwork from the Inside:

Sealing ductwork from the inside out is a much more complicated process and will likely require hiring a professional. Essentially what they will do is mist the inside of the duct with a liquid rubber sealant.

The contractor will start by removing the grilles from the supply and return registers and plugging them with foam rubber and wide strips of tape. Next, they’ll pressurize the duct system with a blower fan and use a computer to analyze the data to determine the amount of air leaking from the ducts.

Using the blower fan, they’ll mist the interior of the duct system with liquid-rubber sealant, which will plug up all the air-leaking holes, cracks, and seams. Afterwards, the contractor will run another pressurized blower test to verify the improved results.

What Happens if You Cover an Air Vent?

Some people believe that covering air vents will keep filtered air from flowing out. But covering your air vent can have negative consequences like the following: 

Disrupts Airflow

A covered vent can not be detected by a heating or cooling system. As warm air is continually pumped into the vent, the return vent cannot pull cool air out of the room; therefore, the airflow in your room is disrupted.

Cause Pressure Buildup

Pressure can be built inside the air duct and HVAC system when air does not circulate properly in a room. This can result in a low flow of air and cracking your heat exchanger, allowing carbon monoxide into your home.

It May Result in a Waste of Energy

Pressure buildup will cause your heat exchanger to get damaged and cause leaks in the air duct. Because of this leak, more energy is consumed to keep your HVAC unit running, thereby wasting energy and increasing your bills.

Different Strokes for Different Folks

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

© 2018 Dan Reed

2. Use Aeroseal to seal ducts from the inside

When leaky ducts are in an accessible area, sealing them doesn’t require any special equipment. Mastic or mastic tape nearly always does the trick. But how do you seal leaky ducts located behind walls?

The answer is Aeroseal. It’s a duct-sealing product that only approved contractors can apply. After cleaning your ducts, a contractor uses specialized equipment to apply Aeroseal inside your ductwork – even the ducts behind walls! Following application, the Aeroseal product hardens within the gaps and cracks inside your ductwork, effectively sealing leaky areas that are otherwise inaccessible.

How does Aeroseal improve airflow? By helping move all the air inside your ducts to the supply registers

When supply ducts leak, a lot of the air that would otherwise make it to a given room just… doesn’t. Aeroseal prevents the air from escaping until it arrives at its destination. If a room doesn’t get enough air right now, it might after applying Aeroseal.

Note that Aeroseal helps seal relatively small gaps and holes. It can’t fill in large holes, seal disconnected ducts, or account for damaged or crushed ductwork behind walls.

And while the cumulative effect of Aeroseal within a home’s entire duct system is to minimize leakage and increase airflow, it’s unlikely to balance the air among different rooms on its own. It can increase airflow when there’s too little, but it’s not a comprehensive fix for an unbalanced system or faulty ductwork.

Bonus: When Aeroseal dramatically reduces duct leakage, it also helps your HVAC system operate more efficiently. You save money and improve airflow at the same time!

Step 1 Caulk or foam seal cracks

Once you have removed the vent cover, you will likely find that the home builder failed to seal the gap between the sheetrock and the ducting. Air-sealing a home is not part of the building process for many contractors and unless the owner specifically requested it, this process is generally skipped.

All we are going to do is run a thin bead of caulk between the ducting and the sheetrock. If the crack is very large, you may need to use an expanding foam like Great Stuff.

I would be cautious with this approach, however, as expanding foam can be messy and once it gets on your sheetrock it can be very difficult to remove.

With this step completed, you have already significantly improved the energy efficiency of this vent. But there’s one more step we can take to further prevent energy loss.

Hidden ducts aren’t always a dead end

Problems with inaccessible ducts can definitely cause airflow problems. Thankfully, there are ways to improve airflow even when you can’t see or touch the problematic ducts.

Is it easier to fix ducts when you can access them directly? Definitely. But that doesn’t mean there aren’t solutions.

Most of the methods we’ve discussed here are reliable and will work for most homes. However, there are exceptions. When ducts are severely bent, crushed, or otherwise damaged, the only way to improve airflow may be to replace the ducts themselves.

Proper airflow, of course, is important for staying comfortable in every room of your home at all times of year.

If you’re concerned about airflow issues in your Atlanta home, give us a holler! Whether or not a hidden duct is to blame, we’ll help you find what’s causing the problem and identify the best solution.


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