Repair/Repalce AC Flex Duct in Attic?

Discussion in 'Community Discussion' started by Huntn, Jan 31, 2013.

  1. macrumors G3


    May 5, 2008
    The Misty Mountains
    Flex AC ducting in the attic- anyone have experience installing this?

    I recently got a new furnace/AC installed. I've noticed that some of my AC duct runs were damaged and had them replace at $150 a pop. There may be others. I'm going to run the AC and check for leaks. My understanding is that the material for running new ducts is very inexpensive.

    I'm considering doing it myself. I spoke with the installer who made it sound simple and it looked simple as I watched them make the repairs.

    Where the duct hits the ceiling vent, smear some glue on the inside, slide it down and attach a plastic tie. Slide the out side part of the duct over and tie it, then smear the glue around the joint. Easy, yes (no)?
  2. macrumors 604

    Aug 9, 2009
    I hope you know that no officially authorized work on ducts can commence without a properly filed Form 27B-6. I have this information from one Harry Tuttle.
  3. macrumors 68040


    Dec 19, 2004
    Not sure why you would glue the joints. Just slide one over the other, secure with tie, make sure the joint is clean and wrap with some aluminum duct tape.

    After my experience with HVAC installers. I wouldn't trust them to install ducting properly. When I investigated some ducts were completely disconnected. They didn't use any ducting tape at all and they installed a filter but the inlet junction feeding it fell off and didn't even fit right. So the system was just sucking in warm damp air from the crawl space making my house humid and smell funny.

    I had to custom fabricate a new junction box from sheet metal. Then go around and seal all the ducts with the aluminum duct tape. Worked great for steel and flex ducts.

    Glue would just make the joints impossible to separate if you ever need to do some work.

    It really is very simple. If you can stick a smaller pipe in a larger one and wrap it with tape. You have all the necessary skills. Actually mounting vents to a wall can be more difficult. But ducting to a vent is simple. Be sure to insulate your ducts.
  4. macrumors G5


    Nov 14, 2007
    1 Geostationary Tower Plaza
    Be sure to do it before summer hits, or you'll be stuck up there in the attic summer heat. Not pleasant.

    Flexible duct work is already insulated. Also, when installing the ducts, be are to stetch them before putting them in place. That way you get the full 25ft.

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