Mastic Sealant vs. Aluminum Foil Tape (for Sealing Air Ducts)


Are your ducts leaking? A leaky duct in your California home may result in uneven cooling during the 105°+ summer heat waves. Duct leaks can introduce more dust and allergens into the air and cause your electric bills to climb. 

If you’re not ready to spend the money on professional air duct sealing and ductwork insulation right now, you can use mastic sealant or HVAC tape for a simple DIY solution. Read on to learn the pros and cons of using mastic sealant vs. aluminum foil tape, a description of each sealant, and how proper HVAC maintenance improves your home’s air quality and energy efficiency. 

In many cases, it’s possible to DIY seal your air ducts, but hiring a professional HVAC tech ensures a more comprehensive duct sealing, even in those hard-to-reach areas of your house. 

What Are Mastic Sealant and Aluminum Foil Tape?

Duct mastic sealant and aluminum foil duct tape are specially formulated sealant solutions made to close gaps and keep debris, pollutants, and moisture out of spaces like your home's air ducts

Mastic duct sealant has a gooey consistency and is usually applied to the duct with a caulk gun or paintbrush. If there’s a gap of ¼ inches or more, you may also need fiberglass mesh tape that matches the sealant you’ve chosen. Duct mastic application can get messy, so a drop cloth, heavy rubber gloves, and old clothes are recommended. 

Aluminum foil tape comes on a roll and looks a lot like everyday duct tape, but it’s extra-durable, malleable, and made with aluminum. It’s a lot easier to apply to your ducts but tends to fail faster as it becomes less sticky over time, especially when stuck to dirty or oily ducts. Choose a high-quality HVAC tape like foil tape, mastic tape, butyl tape, or other heat-approved options that have the Underwriters Laboratories (UL) logo.

Why Is Sealing Air Ducts Important?

Studies have proven that leaky ducts can reduce your heating and cooling system efficiency by up to 20%, which can mean a less comfortable home and higher energy bills. 

Split or cracked ductwork can circulate dust, hair, and dander, reducing the air quality in your home — especially if you don’t have a whole-home air filtration system to remove intrusive microscopic particles from the air. 

Mastic Sealant vs. Aluminum Foil Tape: Pros and Cons 

Mastic sealant and aluminum foil tape are both useful for sealing ductwork, but each solution has benefits and drawbacks.

Pros of using mastic sealant:

  • An excellent, long-lasting barrier 

  • Works best for sealing ducts 

  • Fully cures in around 24 hours

  • Lasts up to 30 years if applied correctly 

Cons of using mastic sealant:

  • Difficult to know if applied correctly 

  • Cured mastic can crack if you rearrange the ducts

  • Messy

Pros of using aluminum foil tape:

  • Quick and easy to apply 

  • A lot less messy than mastic sealant

  • Lasts for up to 5 years

Cons of using aluminum foil tape:

  • Tears and wrinkles easily, which affects the sealant properties

  • Eventually becomes less adhesive and falls off

  • Too many types with varying qualities

  • Sometimes more expensive than mastic sealant

  • Less effective around the sharp and irregular corners of rectangular ducts

Which Is Right for You? 

Deciding between mastic vs. foil tape when sealing air ducts depends on your comfort level with the material and whether you’re looking for an easy (but temporary) solution or a more involved, long-term process. 

If you’re considering whether to DIY your duct issues or call a professional, it may be smart to choose an expert who can give a thorough inspection, clean and insulate the ducts properly, and ensure no small cracks or gaps are missed, especially in the hard-to-reach areas of your home. 

Call Service Champions 

No matter which sealant you choose for your ducts, make sure you choose a high-quality product and clean the application area first. If you have any doubts, don’t hesitate to call Service Champions to schedule a professional air duct leak inspection. Not only can we seal the ductwork so it works like new, but your technician can also clean and insulate your ducts for added efficiency and improved indoor air quality. 

We know that needing ductwork repair isn’t always in the family budget, so we provide complete estimates and financing options before we start the work. We treat all our clients like VIPs, but if you join our MVP membership plan, you’ll also receive priority service response times, special discounts, and regular maintenance, with a 20% discount on all repair parts and services. 

Service Champions is known for trustworthy, on-time home service throughout the East Bay, South Bay, and Sacramento areas. For more information on PureFlow™ duct systems, you can contact us at 800-5-CHAMPS, or schedule your free consultation or duct inspection today. Our team is well-versed in ductwork sealing and can advise you on the best course of action after a thorough examination.

Frequently Asked Questions

Is aluminum foil tape safe to use on air ducts?

Aluminum foil tape is the best tape for sealing ducts and is one of the easiest products to apply if you’re doing a DIY home improvement project. 

Can I use regular duct tape to seal air ducts?

Despite their misleading names, regular duct tape or “dust tape” aren’t good options for sealing air ducts. These products are not made to stand the test of time and fail to provide the barrier you need to keep your conditioned air from escaping and dust, allergens, pests, and microscopic particles from getting in.

Which type of tape or sealant is better for DIY duct sealing?

It depends on the type of DIY project you’re doing. If you’re trying to decide between foil tape vs. mastic sealant, consider the scope of the project. 

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