Battle of the Tape: Duct Mastic vs. Foil Tape

Battle of the Tape: Duct Mastic vs. Foil Tape featured image

October 08, 2017 / by Gregg Cantor / In Green Construction , Home DIY Tips

This post was originally published August 25, 2014 and has been updated with additional content, resources, and images.

Check out our infographic on choosing the right tape for your home improvement project here:

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Ducts within your home can spring leaks for a wide variety of reasons, and at any time, making it a somewhat tough problem to anticipate. That’s why it’s important to have your HVAC system regularly maintained. Still, if you suddenly have a higher-than-average energy bill, your air conditioner or furnace seems to have to work harder to cool or heat your home, or some rooms are noticeably different in temperature or stuffier than others, you may have leaks in your ducts. These leaks within the home can be costly, make your appliances wear out faster, make your home less comfortable, and waste energy over time. In fact, leaky ducts can be one of the largest energy wasters in the home that hinders your attempts at cutting down your energy bills.

Luckily, the ducts that run through your home can be sealed with either foil tape or duct mastic, and every DIY master or contractor has their own preference for what they use when working on residential ducts. Both of these options have their benefits and drawbacks, and just like any project, a professional assessment can go a long way toward ensuring the work is done right and will last well into the future. Here are a few pros and cons of both approaches.

image of duct mastic

Duct Mastic

Duct mastic is a gooey material that can be easily applied using a paintbrush and is readily available at most home improvement stores. Mastic can be applied generously to duct joints and leaks and is a great option for ensuring that the seal will not fail over time. Probably the biggest upside of using mastic is that it is a great choice for those hard-to- reach areas and sharply angled duct joints.

Unlike with using tape, you do not necessarily have to make sure the area is clean before using mastic. There is also no risk of mastic delaminating or stripping off over time. The biggest downside to using mastic is that it can be messy when you are applying it. We always recommend wearing old clothes and rubber gloves when sealing ducts with mastic.

image of foil tape

Foil & Metal Tapes

To fill in holes and gaps, flat metal tape coated with an adhesive is a great choice. Foil tape should only be used for sealing. Quality tapes can be hard to find and must often be purchased at specialty heating stores. Purchasing low quality tapes from home improvement stores is not recommended because there is a high risk of failure after only a few years.

Professional quality tape will stand the test of time. Tapes are much cleaner than mastic, but they are a bit more expensive to purchase. It is also recommended that you clean the area before using any type of tape to seal. For long sections of hard, round ductwork, taping can be an acceptable practice, but irregular surfaces and dirt or dust can compromise the application.

A Word of Caution

The term “duct tape” is quite misleading. Although the name of this product makes it sound perfect for the job at hand, never seal ducts with duct tape. Duct tape is not approved for use on ducts and, despite the fact that it works great for a variety of heavy-duty projects, doesn’t stand up to the conditions of an HVAC system. At Murray Lampert Design, Build, Remodel, we prefer to use duct mastic to seal and repair ducts. We like it because it stands the test of time and makes it easy to fill in those irregularly shaped areas of ductwork. If you have a leaky duct to repair, consider your unique circumstances and which material you feel most comfortable working with. A word of advice with either option: choose a high-quality product. Don’t hesitate to ask someone at a home improvement store for their recommendation on the best product for the job your trying to accomplish. For quality HVAC installations and service, I recommend Mauzy Heating & Air Conditioning in San Diego.

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