Properly Seal your Duct Work to Save Money
Sealing your duct work is a great way to improve the energy efficiency of your home. Ducts run all through your home transporting hot and cold air. The less conditioned air lost en route, the better for your home and your wallet.
Benefits of Sealing your Ducts
Aside from being more comfortable, properly sealed ducts have some great advantages.
- Save money: Your HVAC system won’t have to work as hard for the same level of comfort. The Energy Star site says that leaky duct work can reduce your HVAC efficiency by 20%.
- Safety: Combustion gases are created by gas appliances like water heaters. Properly sealed ducts prevent combustion gases from leaking and remaining inside your house.
- Improved Air Quality: Leaky ducts carry dust, chemicals, and other items throughout your home. Sealed ducts help improve the indoor air quality of your home and keep your duct work clean
- Save the Environment: Lower HVAC energy requirements mean less pollution. ‘Nuff said.
Duct Problems to Look For
Here are some common trouble spots to look for.
- Duct connections: Make sure all the ducts are securely connected to registers and grills.
- Kinks: Flexible duct work may develop kinks that restrict air flow. Check that all the flexible ducts are tidy and kink-free.
- Duct leaks: Seal all duct connections with mastic, metal tape, or an aerosol-based sealant.
How to Seal Ducts
Sealing duct work is easier for new homes but if you have access, any DIYer can do this job.
Sealant Material Options
- Mastic – Mastic is a gummy adhesive that dries solid. I suggest using a water-based mastic as they release less fumes. Find a UL-181 rated mastic. These mastics are more flexible, longer lasting, and adhere to ducts better. Mastic is your best option to seal your ducts.
- Foil tape – This is aluminum foil tape with adhesive on one side. It should also be UL-181 rated.
- Aerosol sealant – This should be installed by a professional. They will pressurize your ducts and inject an aerosol sealant to plug leaks.
Begin by inspecting your duct work. Make sure everything is securely connected and fix any kinks you encounter. Turn on the HVAC system and try to feel out any leaks. Wipe the duct clean before sealing. Apply the mastic with your hand or a trowel but be careful of sharp edges. Use enough mastic to create a continuous coating with a 1/2″ overlap around any hole or joint.
Don’t Use Duct Tape!
Duct Tape is a a vinyl, fabric-reinforced, tape with adhesive on one side. Over time, duct tape will dry, crack, and eventually fall off. It’s not a good permanent solution.
What do you think? Ever notice air leaks? How did you seal them?
Image courtesy of Dano
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9 Responses to Properly Seal your Duct Work to Save Money
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December 5th, 2008 9:44 am
When would you use mastic versus foil tape?
I have an unfinished basement, so I attacked my HVAC with foil tape at all the connections, and a few spots on the pump itself.
Would you also recommend insulating the ducts?
December 5th, 2008 10:54 am
@Chris, Mastic will provide a better seal than foil tape. It’s messier but more effective. Foil tape can still fall off given enough time and you need to pay extra attention to sharp corners that can pierce the tape (and become a leak). With that said, it’s still a good option but you may want to check it periodically to see how it’s holding.
You should definitely insulate your ducts especially in unconditioned areas like attics, crawlspaces, and garages.
December 5th, 2008 11:22 pm
Ethan,
Funny you should say at the end not to use duct tape….let me tell you why. This summer were I work, it didn’t seem like the 2 air conditioning units were cooling our trailer down. Yes I work out in a trailer. Well maintenance discovered that the duct work was leaking and the cold air was staying in the ceiling. Guess what the company they had fix it used. Good old duct tape and I think they did use some kind of adhesive spray. Well I guess it will last for bit. Interesting read though.
December 6th, 2008 4:34 am
How ironic that the only thing duct tape is not good for is actual ducts. Does that mean I shouldn’t use masking tape for my next Halloween costume?
December 6th, 2008 9:40 am
@Lisa and Why S – Well at one point it was used on HVAC systems but over time has become outdated.
I had a friend make an entire Halloween costume out of duct tape. He even had a cape and holder for more duct tape.
April 2nd, 2009 11:33 am
I have no access to my duct work as they are covered by blown insulation in a very tight crawl space. I get lots of dust in my home that I’m sure is coming from the insulation (looks like snow) . How can I seal the leaks without taking out all of the insulation material?
April 3rd, 2009 4:15 pm
@mike, there are aerosol duct dealers. I think the company will pressurize your duct work and spray in this sealant to plug up any leaks. Not sure how well it works or how much it costs. Let me know how it goes.
October 22nd, 2009 4:27 pm
I had the areoseal done in my house the leakage started at 650 cfm and they got it down to 50 cfm and I felt a bigger difference with that than I did with a 90% furnace
December 26th, 2009 10:18 pm
I have an unfinished basement in a new home I just bout in August 2009. I say the duct work need some extra attention in completely insulating it. I used foil tape knowing duct tape was insufficient. I’m going to use duct mastic on the big cracks and gaps.
My question is; I wanted to make my home as efficient as possible. I thought I was doing the right thing by putting foil tape on the ducts. Now that I know about mastic, I’m wondering if I made the wrong decision. Should I rub mastic over the tap or what should I do now that I already have foil tape attached to the ducts. Should I cut the tape and add the mastic? The tape is to strong to just remove. What should I do to make sure my house is getting the best attention to my heating and cooling bills?
Wayne B
Columbus, Ohio