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Why Duct Tape Can't Solve Everything

A few years ago, my car overheated and I found a crack in the top of the radiator that was pouring out coolant as fast as it could. I needed to get to the shop so I slapped some duct tape over it to try and stop the flow on my way to the mechanic. Of course, this patch wasn’t going to hold. Since duct tape (cloth-backed rubber adhesive tape) can’t handle the extreme temperatures all that well, it fails readily. The extreme hot and cold temperatures found in your duct-work will lead to a failure quicker than you might expect. This is why you should always consult a professional when you need to seal damaged ductwork or install new ventilation systems.

What’s the Alternative?

Both butyl duct tape and oriented polypropylene duct tape are stronger and have longer lifespans than hardware-store tape, but these tapes are more expensive and are not guaranteed, especially if applied incorrectly or by an inexperienced person. That said, you should never try to repair or seal ducts on your own using duct tape of any kind. You are more likely to damage your system than fix it.

The International Residential Code (IRC) includes requirements for duct tightness as follows:

  • The 2006 IRC section N1103.2.2 requires that “Ducts, air handlers, filter boxes and building cavities used as ducts shall be sealed,” while IRC section M1601.3.1 requires that “Joints of duct systems shall be made substantially airtight by means of tapes, mastics, gasketing or other approved closure systems.” Hardware-store duct tape is not an approved tape.
  • Section 403.2.2 of the 2004 International Energy Conservation Code (IECC) requires that “All ducts, air handlers, filter boxes, and building cavities used as ducts shall be sealed.”

Professionally installed ventilation systems typically use a combination of gaskets, sheet metal screws, and mastic with mesh tape for sealing purposes. The mastic adhesive used is a non-hardening material with a consistency similar to peanut butter. It’s very messy to work with which is why most homeowners prefer to use a gasket and some brand of duct tape. Unfortunately, as we mentioned before, those seals tend to reopen over time due to the limitations of hardware-store duct tape. If you want a secure duct, whether rigid or flexible, using a mastic adhesive is the way to go, every time.