How to Seal Leaks in Duct Work

There are a lot of very expensive ways that heating and cooling can go wrong, but occasionally homeowners are delighted to find a fix that works—and doesn’t cost a fortune!

Yancey Lowe, general manager of Utility Service Express, has prepared a video to teach how to deal with air leaks in duct work. It may not be something that everyone thinks about, but you can lose a lot of energy through leakage.

What is it?

Duct work is actually composed of a series of separate pieces of metal that are connected together for air to pass through. It probably looks familiar to you from your own basement. What occasionally happens is that as the duct work ages, shifts can occur as the building itself settles (houses are settling all the time, we just don’t generally notice it), and the tape that connects the different pieces of the duct work can shift as well, which means that it will peel or even fall off.

Safety first

This isn’t just an economic issue, it’s a safety one as well. In the summer months, it’s not really a problem and you might not even notice that anything is wrong. In the winter, though, there is a particular fire danger that you need to be aware of. Because one of the ducts being connected is the flue pipe. What passes through it is the air that’s coming directly from the furnace that needs to be directed outdoors. It gets very hot and is potentially dangerous, so be sure to check all your duct work from time to time. You can leave the unit on when you seal the leak, but you’ll want to be careful and not make any direct contact with the hot metal. You may also want to turn the unit off.

What you want to do is feel around to see what’s up with the connections, any of the obvious places where metal is attached to metal, and feel for air leaks. You can usually feel it right away of there’s any air escaping. Even if it’s a small leak, remember that it will take away from your machine’s efficiency and its ability to heat or cool your home comfortably and economically.

Foil tape

What Lowe suggests using to seal the leak is something called foil tape that is generally available at local hardware stores. He says that it’s both reasonably inexpensive and also relatively easy to find.

It’s important to be aware that there are different kinds of foil tape, so read the labels when you’re shopping and select one that is labeled for HVAC use. The tape has a paper backing.

First you want to check and see how large the leak is that you want to seal. In the demonstration, it’s about three to four inches. So just cut off more than you need so you have good coverage (in this case, five to six inches), and then peel the paper backing off the foil tape.

Let the tape down, checking the air as you go and just firmly apply the tape to the spot where you’ve located the leak. Press the tape down and then go around it on all sides with a steady pressure so that you have a nice seal and can tell that there isn’t any more air coming through.

This may seem like a simple and obvious fix, but Lowe is clear that if it’s done over all the duct work you can access, you’ll increase your machine’s efficiency so that all of its energy is spent heating or cooling your house.