Archive for the ‘Energy Efficiency’ Category

Greentaining: Sealing My Leaky Ducts

air duct sealed with metal tape

air duct sealed with metal tape

When our friend, Richard, an HVAC professional, installed a new air duct in our new house a few weeks back he suggested we seal the leaks in our duct system.

“Feel this,” he said, putting his hand over a joint in a duct and waiting for me to do the same. I did so and felt a rather strong current of air. “Feel that air? Your system would be a lot more efficient if you sealed these with tape. You can do it yourselves with duct tape—that is why they originally called it duct tape—though you’ll need to replace it at some point, or you can use a metal tape like I’ll use to seal this vent I’m installing.” (paraphrase)

Aside from efficiently using energy, which is always important to me, I wanted comfortable, evenly heated and cooled rooms, a high priority to my temperature-sensitive self.

Of course, it always takes two people telling me to do something before I buy in.

Today that second “person” was Energy Star.

According to, “Sealing and insulating ducts can improve the efficiency of your heating and cooling system by 20 percent or more. Accessible ducts, such as those in attics, basements, crawlspaces, and garages, can be sealed using a specialized sealant called duct mastic available at home improvement stores (duct tape is not recommended).”

old duct tape from my air duct system

Old duct tape from my air duct. This is why not to use traditional duct tape.

The duct tape they’re referring to is the cloth-backed rubber adhesive duct tape of which we quickly think. Of course, I didn’t listen to that, either, and initially began sealing my ducts with duct tape until I found an old piece of duct tape, loosely hanging from a pipe, that illustrated why standard duct tape is a poor choice. (See my photo.) Ewe.

Duct Sealing: Do You Need To Do It, and How?

aluminum tape for sealing leaky ductsSo check out your air system (even you apartment dwellers). Turn on the air and put your hand in front of the metal joints. Do you feel air?

If you do, go to your local home improvement store, pick up some aluminum foil tape (Nashua Multi-Purpose Aluminum Foil Tape 322 HVAC, $6.58 at You can use mastic tape or mastic sealant instead, if you wish. We’re literally going to tape over the leaks to prevent air from blowing out of the system where it shouldn’t.

Next, clean the joints on which we’ll apply the tape with soap and water.

Begin sealing the air leaks by taping all the duct joints you can access. Even if it doesn’t feel like air is escaping doesn’t mean it won’t in the future, so tape around the duct in every place you can reach where two pieces of duct join.

Tape all joints on the furnace including the corners.

Finally, seal vents and registers where they meet floors, walls, and ceilings.

That’s it! It may not be perfect (less easily accessible leaks may still exist) but you’ll already enjoy a more efficient air system and, likely, more comfortable rooms.

Easy peasy.


What do you think? Have you sealed leaky ducts either yourself or by an HVAC professional?

What other easy energy efficiency projects have you done?

Additional Resources:

US EPA Energy Star “Duct Sealing” Brochure (printable)

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