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2 Easy Ways to Seal Your Leaky Ductwork (With Pictures)

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Dan has been in the HVAC industry for 23 years, with experience ranging from installation and service to sales and distribution.

A gap in your duct work as small as this can still leak large amounts of air.

A gap in your duct work as small as this can still leak large amounts of air.

How Do You Fix Leaky Ducts?

Homeowners are looking for any way possible to shave money off their energy bills as well as not waste energy to minimize their ecological footprint. Most owners of newly built homes have the luxury of knowing that their home is "up to snuff" since codes and regulations in many municipalities have made it nearly impossible to build a home that is not energy efficient, but those who own older homes have improvements to make if they want to cut down costs and waste.

While some of these improvements are expensive and typically require a skilled tradesman to perform, there are some that are quite simple, cost very little, and just about anyone can do. One of them is sealing up leaks in their ductwork.

There are two very cheap, very easy ways to fix your leaky ductwork yourself; HVAC tape and duct sealant.

What Is HVAC Tape?

HVAC tape is basically any tape rated for use on HVAC systems. While there are certain tapes for certain jobs, they are all considered HVAC tape. For the purpose of sealing air distributing ducts, I've provided some images and descriptions of different types of tape that are commonly used on both residential and commercial applications.

You probably noticed that good old-fashioned duct tape isn't mentioned and that is because while duct tape had been the most commonly used for decades, it has begun to fall by the wayside in the HVAC world. While duct tape is strong, it simply begins to dry out and fall away, leaving leaks over time where the newer foil tapes do not. Don't worry, there are still a million other ways to use our beloved duct just won't be to seal your ducts.

I use this Polyken 337 foil tape (also pictured above) because it's wide enough to bridge even the larger gaps but still can be cut down to size. It's also the correct thickness and sticks well.

Now let us take a look at these images of common leak points and the basic foil tape I applied to seal them. I chose basic tape because it seals great, tears easy, and I can cut it if I ever need to take the duct apart again.

Option 2 - Duct Sealant (Not Duct Seal)

Pick your poison. Seal your duct by the gallon or by the tube. Whichever way suits you best.

Pick your poison. Seal your duct by the gallon or by the tube. Whichever way suits you best.

Duct sealant is another product that is commonly used to seal up duct leaks. This pasty, thick, paint-like substance can be applied to cracks and gaps in your ductwork with a caulking gun and spread with a paintbrush, or if using a gallon pail, just scooped and applied directly with the paintbrush.

I recommend using a water-based sealant as it holds up well and cleans up easy also. Trust me when I say easy clean up is important. I didn't pay much attention to this once and ended up shaving off my arm hair as a result. It was not my proudest moment. Moving on...

Mastic sealer is probably the longest lasting option for sealing your ductwork, but I would consider whether or not you'll ever need to access the area again before using it. In spots that you may want to open up again, like near the evaporator coil that you may want to have cleaned or an end cap where you may want to clean your ducts, I would use one of the tape options.

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.

Do It Yourself Duct Sealing

There is not a whole lot that I can tell you about duct sealing technique. It really is a pretty self-explanatory process. Apply the tape or sealant over the holes and seams...pretty simple right? There are, however, a few things that might help your job go smoother, be more effective, and last longer.

  • Use a water based mastic.
  • Wear rubber gloves and old long sleeve shirt if using mastic. (Maybe a hat, too.)
  • Whether you use tape or mastic, make sure the surface of your sealing is clean and dry.
  • Tapes will stick much better if they are warm. Make sure your tape is at least room temperature and maybe even apply the tape while the heat is running.
  • Every little bit counts. Cover all the holes and seams you can.

The Benefits of Sealing Your Ductwork

Many will argue that air escaping your ducts is still in the house, so the energy is not really lost. They claim that little gaps, holes, and seams don't amount to much loss anyway. I beg to differ.

If you add up the square inches of leakage in an older home's ducting, you'd find that a large majority of homes would be losing roughly the same amount of air as cutting a baseball-sized hole in the duct. It is typically leaked into an unconditioned area like a basement or attic where it is not needed. So while you wonder why that one room is so cold or hot all the time, consider that these little leaks can add up to roughly the same amount of air needed to heat and cool a room.

The other consideration here is that we're not only sealing the air in but the dust out. Seal both the supply and the return air ducts. Return air duct sucks air in so sealing them keeps smelly basement air and/or attic dust from creeping into our air supply also. Sure, our filter will get most of that but then you'll be changing your filter and cleaning your ductwork more often.

This all leads back to the benefits of energy cost savings, a smaller environmental impact, and better indoor air quality. Even if only one of these benefits appeals to you then it would be worth the time and little cost to seal up your ducts.

~ We're all in this together ~

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


Dan Reed (author) on May 08, 2018:

Thank you Robie! One thing you might try to balance out temperatures in your house is to leave the fan running all the time. I run mine about 320 days a year and it evens rooms out quite nicely while costing next to nothing. You may even find the A/C or furnace run just a bit less on milder days. I know it sounds weird to run the fan all the time, especially in the winter, but it works.

Robie Benve from Ohio on May 08, 2018:

Great information Dan! Now I need to go look at my ducts, trying to figure out why two of my rooms are always the wrong temperature. Thanks!