Put a lid on too-high heating bills
Your home's HVAC ductwork hides behind floorboards or drywall, so you only think about it when it’s not functioning correctly. If you’re replacing old ducts with new ones or want to remove a register from an unused room, you’ll need to cap off the duct to promote efficient airflow and avoid overloading your HVAC unit. This guide will teach you how to cap off a duct in minutes.
Duct caps come in many different sizes and shapes to fit a variety of HVAC ducts. To find the right size for your needs, measure the duct you want to cap off and find an end cap that will fit. Round end caps range in size from four to eight inches in diameter, while rectangular ones range from eight inches by 12 inches to 24 inches.
Once you have the correct duct cap, attach it to the end of the duct you want to seal off. You’ll want to ensure a snug fit since any gaps will let air escape through the duct. If it’s the wrong size, exchange it for another. Many home improvement stores accept returns if you accidentally purchase the wrong size. Attach the cap to the duct using sheet metal screws.
Finally, seal the duct cap to ensure a tight fit. Use mastic or duct tape to seal the duct completely. Mastic is the more expensive option but is long-lasting, so you won’t need to reapply to ensure the seal remains. Duct tape is a cheap and DIY-friendly option, but it will eventually lose adhesion and must be replaced.
Capping off a duct is a relatively simple project, but without the proper knowledge, you could make several potential mistakes. Here are some of the biggest mistakes to avoid when capping off a duct.
Buying the wrong size cap
Not sealing the cap properly
Skipping the cap and taping the duct closed
Using the wrong screws to secure the duct cap
There are several times when you might need to cap off a duct. For example, if you’re removing a vent from a room you no longer use, you’d need to cap off the duct after removing the vent to maintain steady airflow in the ductwork system. Capping off a duct may also be necessary if the ductwork is damaged and you’re replacing it with new ductwork in a different part of the room. Capping off the old duct ensures that the air is directed to the new vent rather than leaking through the old one.
Capping off an HVAC duct is an easy DIY for a handy homeowner. As long as you can find the right size cap for your duct and install it properly, being careful to seal it thoroughly, you can certainly do this job yourself.
However, if your ductwork is a non-standard size, you might need an HVAC professional to make a custom duct cap using sheet metal. The pro can then install the custom cap to seal off your duct, and they’ll ensure it’s done correctly so there are no leaks. An HVAC duct installer near you can also handle this job if you don’t feel comfortable tackling it as a DIY project—especially if your ducts are inaccessible.
I normally do not leave reviews, but my experience with Worthington Air was extremely frustrating and disappointing. About 30 days ago, I had a consultation done for an HVAC replacement and was quoted approximately $15,079. Based on that quote, I applied for financing through their company...
ARS Columbus Worthington AirGreat company! Price was competitive, technician showed up on time and completed the job (exterior electric Radon fan replacement) quickly. Would hire them again.
MaGen Property Inspections and Radon MitigationRaven and crew does absolutely fantastic job. They are very professional if any concerns were to occur with any of her work she always took responsibility and finished out with a great job. I have worked with her business for a year and have always been satisfied. Very trusted business and...
Creations of Transformation LLCI would recommend this company to anyone! He showed up on time, was friendly, completed a very difficult repair on our dryer vent cover, was responsive, and pricing was extremely fair and competitive. I would have him back to do any of our repairs or cleanings without hesitation!
U.S.A. Dryer Vent, LLCAce Fireplace Services' chimney sweep service is truly exceptional. They used advanced technology to ensure a thorough cleaning process, and my chimney has never looked better. I highly recommend their services.
Ace Fireplace ServicesThe technician was very professional and friendly. He answered all my questions and was very thorough. He left the fireplace area very clean . He inspected from the roof and advised me as to other work that might need to be done. There was no pressure there. I was very satisfied with the...
Supreme brick & chimneyExcellent experience with hiring Tether House to Mount our 77’ Samsung TV in our bedroom. Fast, friendly, and knowledgeable. Highly recommend.
Tether HouseOn time, clean and finished fast. Windows seem sturdy and the finish is good. Caulking was done with no smudges. Would recommend.
Window Depot USA of Central OhioGreat job...edging and pre clean up went well with a great job with seal coat. Friendly, efficient and professional.
All Star Paving and SealingGood workers and they do a good job.
Mira ConstructionFrom average costs to expert advice, get all the answers you need to get your job done.
Curious about air duct cleaning costs? Get insights into pricing factors, benefits, and how to tell when it’s time for a good cleaning.
If your energy bills have increased or your home isn’t as comfortable as it used to be, use this duct sealing cost guide to see how much a solution will total.
Discover the true duct replacement cost for your home. Learn about average prices, key cost factors, and tips to save on your ductwork replacement project.
A blocked air duct can impact indoor air quality and raise energy bills. Learn how to check for blocked air ducts with these easy DIY methods.
Tackling unwanted odors from indoor plants can be tricky. Learn how to use a carbon filter in your duct fan to improve air quality.
Do you detect a strange smell coming from your home’s ductwork? Learn how to remove odor from air ducts with this step-by-step guide.
