You can’t use duct tape on ducts. Huh? How did that happen? Well, the general pupose repair tape we now call duct tape was originally “duck tape,” likely because it started out being made from duck cloth, and the name morphed to duct tape over the years. But it is not the right material for sealing and repairing ducts for two reasons: 1) it is not approved by the building codes for use on HVAC ducts, and 2) it doesn’t have the right type of heat-resistant adhesive for a long-term tight seal. 

    Any tape used for HVAC ducts must have the “UL 181” marking on the tape. The 181 is a designation given for an approved tape by Underwriters Laboratories after testing it for resistance to fire, moisture, mold, extreme temperature, impact, tension, and leakage. The two most commonly used types are UL 181A-P for rigid ductwork and UL-181B-FX for flex ducts. Repairing duct leaks with ordinary duct tape is only a short-term solution to the long-term problem of ducts leaking as they age.

    Also see our articles What is the average life expectancy of house a/c and heating ducts? and What is a jump duct? and What are the problems with underground return air ducts?

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  To learn more about heating and air conditioning systems, see these other blog posts:

• How can I find out the SEER of my air conditioner? 

• My air conditioner won't turn on. What's wrong? 

• How can I find out the size of my air conditioner? 

• How can I tell whether the condenser (outdoor unit) is an air conditioner or heat pump? 

• Where is the air filter for my central air conditioner and furnace? I can’t find it? 

• Does an old air conditioner use more electricity as it ages? 

• How did homes stay cool in Florida before air conditioning? 

• What is wrong with an air conditioner when the air flow out of the vents is low?

• Why has the thermostat screen gone blank? 

• Why does it take so long to cool a house when an air conditioner has been off for a while? 

• Why is my air conditioner not cooling enough? 

• What are the most common problems with wall/window air conditioners?  

• Will closing doors reduce my heating and cooling costs? 

   Visit our HEATING AND AIR CONDITIONING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.