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  1. #1
    Join Date
    Jan 2010
    Location
    Miami, FL
    Posts
    11

    fabricating duct board inside out?

    Hello,
    I read somewhere else on the internet that fiberglass duct board can be fabricated inside out so that the foil side would face the airstream. Is this really possible? I would think this would prevent fibers from entering the airstream, provide less resistance, and make a better surface for future cleaning. Would there be any downsides to this though?

  2. #2
    Join Date
    Jul 2009
    Location
    Plant City, Florida
    Posts
    2,198
    Quote Originally Posted by tmb5107 View Post
    Hello,
    I read somewhere else on the internet that fiberglass duct board can be fabricated inside out so that the foil side would face the airstream. Is this really possible? I would think this would prevent fibers from entering the airstream, provide less resistance, and make a better surface for future cleaning. Would there be any downsides to this though?
    How do you plan on taping it?

    I am sure an inspector would red tag it as well.

    As far as downside,

    It was not approved for use that way, there is a reason the engineers spent a lot of time and money figuring out how to use ductboard.

  3. #3
    Join Date
    Apr 2006
    Location
    Houston, Texas
    Posts
    40
    the outer liner is like a vapor barrier, but also holds the duct together when you make your cuts to fold duct. If you flip it over you will cut the foil causing the duct to fall apart.

    Are you simply sealing a chase are actually trying to run it as supply duct?

  4. #4
    Join Date
    Mar 2005
    Location
    Houston, Texas
    Posts
    11,873
    I've done return air chases that way.
    Can't say as I'd use it that way for a supply though.

  5. #5
    Join Date
    Jan 2010
    Location
    Miami, FL
    Posts
    11
    I was considering having a supply trunk line fabricated this way. I am not an installer, but a consumer who is concerned about fiberglass in the airstream from duct board. So the idea of turning duct board inside out may be completely unfeasible. I'm not really sure. I would really just like to use metal duct work but I don' think I can afford it and I don't know of any other alternatives. I've heard of coating the interior of the duct board with something like Foster 40-20 but I'm a bit leery of this as well. Any suggestions would be greatly appreciated.

  6. #6
    Join Date
    Oct 2009
    Location
    Raleigh, NC
    Posts
    799
    How is it that a significant amount of fiberglass fibers get into the airstream? I can see there being some on the first minutes of the first startup, but after that I cannot imagine that any significant amount of fibers would come loose into the airstream unless the ducting was disturbed in some way. If there were constantly fibers coming loose, then the ductboard would slowly erode away to nothing!

  7. #7
    Join Date
    Mar 2005
    Location
    Houston, Texas
    Posts
    11,873
    Quote Originally Posted by tmb5107 View Post
    I was considering having a supply trunk line fabricated this way. I am not an installer, but a consumer who is concerned about fiberglass in the airstream from duct board. So the idea of turning duct board inside out may be completely unfeasible. I'm not really sure. I would really just like to use metal duct work but I don' think I can afford it and I don't know of any other alternatives. I've heard of coating the interior of the duct board with something like Foster 40-20 but I'm a bit leery of this as well. Any suggestions would be greatly appreciated.
    Flip a quarter. I wouldn't worry about it. Duct board has been around many years now.
    If you think it's that big of a problem, bite the bullet, and get metal duct,externally insulated.
    Really, don't worry a lot about this.

  8. #8
    Join Date
    Jul 2009
    Location
    Plant City, Florida
    Posts
    2,198
    Quote Originally Posted by tmb5107 View Post
    I was considering having a supply trunk line fabricated this way. I am not an installer, but a consumer who is concerned about fiberglass in the airstream from duct board. So the idea of turning duct board inside out may be completely unfeasible. I'm not really sure. I would really just like to use metal duct work but I don' think I can afford it and I don't know of any other alternatives. I've heard of coating the interior of the duct board with something like Foster 40-20 but I'm a bit leery of this as well. Any suggestions would be greatly appreciated.
    If you don't want fiberglass and don't want to pay for metal ductwork, don't buy an A/C system.

    Why are you so concerned about fiberglass duct?

  9. #9
    Join Date
    Sep 2002
    Location
    Northeast Ohio
    Posts
    4,842
    While I'm not a big fan of duct board and use it minimally, once eveything is cut in and sealed, migration of fiberglass particles is almost nill. Don't sweat it, if you can swing it go with metal duct wrapped otherwise go with the duct board.
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


  10. #10
    Join Date
    Nov 2004
    Location
    Naples, Fla.
    Posts
    1,403
    Looking at your return address (Miami) you are making a serious mistake even thinking about reversing the duct board. As stated it would fall apart, the outer layer is all that holds it together - but beyond the obvious, even if you Rube Goldberg’d an installation like this you would have an extreme mold & sweating issue to deal with. The outer foil layer is the vapor barrier - if you invert the board, moisture would freely migrate to the foil (now the coldest part) and condense.

    Duct board properly installed will outlast you & your children - it is heat sealed on the inside to prevent degradation and better board is even approved for clean rooms and surgical centers.

    Spend your time finding a good contractor not making design changes you are unqualified for.

  11. #11
    Join Date
    Jan 2009
    Location
    Indiana
    Posts
    3,228
    Quote Originally Posted by coolguysfl View Post
    better board is even approved for clean rooms and surgical centers.
    check local codes...there are no varieties of duct board allowed in my county for anything.
    lined returns and insulated supply only..im sure they have a good reason for doing this, what is is i am not %100 sure...%75 percent yea but not 100

  12. #12
    Join Date
    Jan 2010
    Location
    Miami, FL
    Posts
    11
    thanks coolguy,
    can you let me know a few of the products that are approved for clean room/surgery as I would be interested in using one of these

  13. #13
    Join Date
    Nov 2004
    Location
    Naples, Fla.
    Posts
    1,403
    Several quality brands out there.... but it must be installed properly, just be sure your contractor can give you address's where you can preview his work & insist on all mastic sealed - you'll be fine.

    BTW --- if IAQ is your concern, do'nt go cheap on your selection of air filters, dehumidifier or UV system


    http://www.johnsmanville.com/insulat...ct_systems.pdf

    http://www.specjm.com/files/pdf/AHS-412.pdf

    http://www.specjm.com/commercial/air.../ductboard.asp

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