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  1. #1
    Join Date
    Sep 2010
    Location
    phoenix
    Posts
    73

    What is the life span of flex duct?

    Some of the neighbors are having problems with their flex duct breaking down. What is the life span of flex duct in a very hot attic in the desert southwest....

  2. #2
    Join Date
    Jul 2007
    Location
    san antonio
    Posts
    51
    Ducks are not as long-lived as geese. The average life span of a domestic duck is 10 years or less.

    As a general rule, the larger breeds of duck have the shortest life spans. Seldom do they live beyond five to seven years of age.

  3. #3
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,170
    there is a gray flex that breaks down.
    looks like someone split it open with a razor knife.
    uv light causes it to break down, and just age.
    I'd guess that in this area this gray flex was installed
    25 years ago.
    now flex has a silver reflective liner that reflects heat
    away.
    life of flex as used in our state's calculations is 30years.
    barring any rodent damage and correct install.
    mine is a hot humid climate.
    so life may vary in different climates.

    can you give more detail?

    best of luck.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  4. #4
    Join Date
    Sep 2010
    Location
    phoenix
    Posts
    73
    details...

    the neighbors (3 of them) have now found leaks in the attic flex duct. 16 inch main trunk lines. If they were anything like mine, they were installed loose. Mine had a 19 foot run and with the duct stretched out it was over 40 feet long. (mine got new metal ducts!!) The failures are in the inner duct. The wire appears to be ripping throught the clear inner plastic. This in turn billows up the outside gray jacket and cools the attic very nicely!!!!
    Attic temps can be as high at 180 or above, as outside temps can be as high as 120. My thinking is that movement (repeated flexing), old age and heat have taken their toll!!!.

  5. #5
    Join Date
    Dec 2004
    Location
    Derby City
    Posts
    3,963
    A poor installation should not reflect adversely on the product, in this case the flex duct. I agree that flex duct, when properly installed in the correct application, can last just as long as a galvanized system.

    Irish
    Everyone has a purpose in life..........even if it's to be a bad example.

    Seek first to understand, before seeking to be understood.

  6. #6
    Join Date
    Apr 2010
    Location
    southern california
    Posts
    535
    Most flex duct is now rated for 200F maximum and has a mfg warranty against defects of 10 years. If your attic is at the temperature you state, you would be better off ventilating the space , replacing ductwork with steel and superinsulating the steel ductwork to reduce heat transmission.

  7. #7
    Join Date
    Sep 2010
    Location
    phoenix
    Posts
    73
    Its not my attic that has issues. I tore that flex duct out last year and replaced it with sheetmetal!!!! I also added a ridge vent, eve vents and gable vents. I am well over the minimum code (by (by 2 times) for square inches of vent space per floor space . My ductwork is 16 inch screwed 8 times at each union, sealed (mastic), taped with aluminum tape (ul listed) and then pressed down with a plastic spreader. Then double wrapped with vapor barrier, r26 of insulation and finally reflective wrapped.

    Mine does not leak, but the neighbors do!!!!!!!!! I was just curious as to the life span of flex duct.

  8. #8
    Join Date
    Nov 2008
    Location
    Chapel Hill, NC
    Posts
    1,070
    We just had out 20 year old flexduct replaced as part of a system swapout. It looked to be in fine condition (a little dirty/dusty). It was the R6 mylar type. If I'd known it was going to look so good, I'd have probably kept it for another 20 years.

  9. #9
    Join Date
    Sep 2010
    Location
    phoenix
    Posts
    73
    you couldnt pay me to keep flex.. the static pressure, at least with out system, droped from 1.25 to .55 when we got rid of the flex...

    we also got a new plenum in the deal. so that may have contributed to the dramatic decrease in the numbers.

  10. #10
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,170
    I've never seen the inner liner fail.
    (there is prolly a lot I haven't seen..LOL!)

    glad that you are satisfied with your ductwork.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  11. #11
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,190

    Old stuff is subject to UV problems

    That is the inner and some outer (PVC) jacket
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  12. #12
    Join Date
    Mar 2011
    Location
    Corpus Christi, TX
    Posts
    49
    All duct work should be inspected regularly and replaced if necessary.

  13. #13
    Join Date
    May 2007
    Location
    Dry as a bone Tucson
    Posts
    4,304
    Quote Originally Posted by genduct View Post
    That is the inner and some outer (PVC) jacket
    This is probably what your neighbors duct looks like. And what genduct is refering to. This stuff was used in the late 80's to the late 90's and should be replaced. It was typically found in track homes that also had polybutelene tubing and you probably have heard about that stuff.

    Some Talk, Some Do
    "keeping condensing pressures low and evaporator pressures high"
    "Some customers are more interested in comfort than energy savings"
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