Duct Sealing: Here’s How You Can Do It Yourself

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Because of our geographical location, Cincinnati has hot, humid summers and cold, snowy winters. This means our HVAC systems work pretty much year-round, so anything that helps them run more efficiently is doubly beneficial. Checking and sealing ductwork can be a DIY project that can result in substantial utility savings for handy homeowners.

What Do Ducts Do?

Homes with a central HVAC system use a network of ducts to move treated air to your living space from the equipment that heats or cools it. Almost always, both the furnace and the AC use the same air handler, often called a blower, to move the treated air through the ducts.

metal Ductwork

Why Check the Ductwork?

The Department of Energy’s (DOE) Energy Star program estimates that the typical forced air system loses approximately 20 to 30 percent of its treated air. It escapes through holes in the ducts and at unsound connection points. That translates directly into an increase in your utility bills even though the level of comfort you’d get if the ducts didn’t leak is about the same.

It may well be that with duct leaks, your equipment never manages to create your ideal environment, no matter how hard it works. You may be used to this and not necessarily know what an ideal environment with ducts that don’t leak is. For this reason, it can be difficult to detect leaky air ducts.

Signs of Leaky Air Ducts

Watch out for these signs of leaking air ducts in your home:

  • Cold or hot air comes from the registers in different rooms
  • Whistling or other noises coming from your ducts
  • Higher than expected energy bills
  • Dust or dirt builds up in your home
  • Higher than average allergy or asthma symptoms in your home

Dust build up may indicate that you need to clean out your ducts, or it may be that leaks in your ductwork is picking up dust and dirt from walls, crawlspaces, or basements.

DIY Duct Sealing

duct sealing with aluminum metal duct tape

Sealing your ducts can save you a lot of money and help improve your indoor air quality. When your ducts are properly sealed, your central air system will no longer be sucking in air from basements, crawlspaces, walls, or attics, grabbing dust and dirt that the air can circulate into your home.

The first step in sealing your ductwork is to inspect all the exposed ductwork in your loft, crawl spaces, garage, and attic. Pay particular attention to long, unsupported runs and flattened areas, as ductwork is easy to crush accidentally. Crushed ductwork can create tears or even airway traffic jams, putting strain on your HVAC equipment. Joints are also failure points, so check behind all registers and where separate duct runs join one another.

Two main products help you seal your ducts: mastic sealant and aluminum foil tape.

Duct Mastic Sealant

Duct mastic sealant is a gooey, rubbery substance that hardens after air drying. It is water-based and can be applied with an old paintbrush. It is relatively messy to apply, but it is less expensive than aluminum foil tape. Mastic sealant is very durable and will hold up for a long time.

Apply duct mastic sealant whenever you have a metal-to-metal transition. This includes joints and seams along straight runs.

Mastic sealant is also useful for sealing the outside of your home around electrical wires and other tiny gaps. If the gap is sizable, you may need to combine liquid mastic with a fiberglass mesh tap when gaps are larger than one-fourth of an inch.

Duct Sealing Tape or Aluminum Foil Tape

metal duct tape for sealing air ducts

Duct sealing tape, also known as aluminum foil tape, comes in a row. It is tape with an aluminum backing, and it can be found in any hardware store. It is sometimes referred to as metal tape.

Using aluminum foil tape is less messy and time consuming than mastic sealant. It is more expensive, and doesn’t last as long as mastic sealant. Ducts that easily get dirty or oily tend to shed duct sealing tape. Tape is useful for sealing holes larger than one fourth of an inch, connecting metal to insulation, and connecting flexible duct to the metal transition of the HVAC system.

To use duct sealing tape, you must first prepare the area. It will need to be scrubbed clean of dust and dirt. Apply the tape carefully and use a squeegee to firmly press the tape to the material so it gets a good adhesive hold. Use scissors to cut the metal duct tape.

Sealant tape comes in both firmer and more flexible varieties. More flexible tape is best for connecting flexible duct or insulation and should be wrapped around several times.

Good duct sealing tape is rated for a wide range of temperatures. Do not use standard duct tape. It is not fire- or smoke-rated and will quickly fail.

Insulating Your Ductwork

Once you have sealed all the joints and connections, any ducts that are not in a conditioned space should be insulated.

Ducts in uninsulated basements, crawl spaces, and other non-conditioned, non-insulated spaces should be insulated. This will help keep warm air warm, and cold air cold. Use duct sealing tape to secure insulation to your ductwork.

Need Help With Your Ducts in Greater Cincinnati?

Duct sealing is a rewarding job for any competent DIYer, but can be tricky without having the right tools or experience. At Apollo, we can inspect and test your air ducts, and check for any missed holes or connections. We offer duct services in Greater Cinncinnati, Northern Kentucky, Dayton, Ohio, and the surrounding areas. In addition to testing, we also offer professional duct cleaning services.

Contact Apollo Home Heating, Cooling and Plumbing for all of your HVAC and home comfort needs.

"Ernie & Mike did a superb job on my new furnace and A/C installation. Despite having more than a day’s work to do, they came in and stayed until the job was done. They were organized, efficient, and protected the rest of the house well. Got both furnace and A/C installed the same day. Ernie was courteous, informative, and clearly knew his job better than anyone I’ve encountered before. The units look so good guests now get The Tour of our new system. Apollo is clearly not a fly-by-night company. I would recommend them to anyone in need of a new furnace and/or A/C."
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"We scheduled an estimate AND a tune-up. We knew something was wrong with our furnace, but hoped we could make it through the rest of the season. Upon telling Bill what our furnace was doing, he warned us immediately what the possible outcome was going to be; a cracked heat exchanger. He watched the flames roll backward, tested carbon monoxide levels, which were so high they meter’s last reading was 5,600 before saying “high”. He immediately shut it down, tagged it, and explained that with levels that high and children in our home he wanted off right away. He continued his inspection and showed us via a camera that not only was it cracked in multiple places, but had holes all over it. He gave us a few options for repairing it; his knowledge as well as genuine concern was beneficial and refreshing. Luckily we also scheduled an estimator, Micah, to come too and we were able to get costs between repairing and replacing (with several options). We decided to replace with a much higher efficiency furnace and one sized properly to our home. Hands down, not only did they both provide us great service and knowledge, but without sounding dramatic, they may have saved our lives. This was our first time calling Apollo, but it won’t be our last."
- Sarah B.
"Apollo is an excellent company. I always receive great service. Alex A. was professional and friendly. He kept me informed during the process of checking my furnace and heat pump to make sure they were working properly. The company makes sure you are notified who is coming and when they are on the way. All my interactions with the company have been wonderful."
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