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  1. #1
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,188
    In my quest for hands on experience, this past weekend,I worked with the duct designer building trunk
    line and distribution boxes out of ductboard for a
    client.
    We used Certainteed R-4 ductboard.Heating system and
    all ducts in attic, flex duct is R-6. All seams were
    stapled, taped with foil tape. Connections to units
    were with Hardcast mastic tape.
    My job was pretty much laborer aka stepnfetchit.
    I was wondering about IAQ and ductboard for people
    with breathing problems and related issues.
    So I have some questions.
    By cutting in to fiberglass to make boxes, will
    that free enough particles to be an issue for the
    homeowner?
    Is there a sealant that should be applied over these
    cuts? If so, when collars are installed into trunk
    line would those areas also be sealed and how?
    Is this overkill?
    Does ductboard come in higher R-values?
    Would this be a cost effective upgrade?
    Is ductboard used primarily for ease (ha) of install?
    I do not see a lot of ductboard on my inspections
    and wonder why.
    Any comments and suggestions are welcomed.
    This is not my regular job, just have that inquiring mind
    thing going on.
    Also I saw that in installing the flex duct that
    it took 2 people to streach the ducts. I was told that
    you have to hold the inner lining and pull the lenghth
    of the duct to unkink before installing.
    I wondered about this because on my inspections I often'
    see one guy installing flex. What do you think??
    Thanks!
    Any suggestions for improvement would be appreciated.
    Goal is 5% duct loss.Will test once home is completed.


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

  2. #2
    Join Date
    Mar 2004
    Location
    Austin, Texas
    Posts
    1,959
    SInce no one else has, I will attempt to address your questions. Duct board is available in 1 inch (R4), 1 1/2 inch (R6) and 2 inch (R8). For ducts installed in an unconditioned space the higher R values are VERY cost effective. In states that have adopted the 2000 Interantional Energy Code with the 2001 amendments, R8 is REQUIRED.

    Studies have shown that airborne fiberglass particles from the duct board are pretty much gone after the first hour or two of blower operation. Those studies were funded by the duct board manufacturer's association, so there are still qustions about the studies. I believe that all the other airborne construction debris is at least as much a problem as the duct board particles. People with breating problems shouldn't hang around a construction site. You can put duct sealant over all those cuts if you want. The question should be, how many are you (or the owner) willing to pay for?

    Duct board is normally used when there is a reason NOT to use flex duct. Some of the reasons would be: flex isn't available that large, duct must be rectangular to fit in space available (like between floors), lower pressure drop is needed, etc. Flex is used for one reason - it is cheap. Flex duct is all that consumers are willing to pay for.

    I've never seem anything that says it takes two people to staighten flex duct. Most flex duct is installed with so many kinks and bends that it appears to indicate flex duct CANNOT be cut. (Why else would a 5 foot straight duct run have a full 25' lenght of flex installed???)

    Good luck on the 5% air leakage through the duct system. It can be done, but it takes more care, sealing, testing resealing, retesting, more sealing, more testing than most people are willing to do.

  3. #3
    Join Date
    Jul 2004
    Location
    new england(conn,ri mass)
    Posts
    17
    I WOULDN`T INSTALL DUCT BOARD IN MY HOUSE IF IT IT WAS FREE. I HAVE SEEN IT BREAK DOWN. AFTER A FEW DAYS OF OPERATION, INSTALL AN AIR FILTER IN THE SUPPLY AND CHECK IN A FEW YEARS. YOU WILL BE SURPRIZED. ALSO, YOU CAN`T INSTALL A HUMIDIFYER WITH DUCT BOARD BECAUSE IT WILL DAMAGE THE INSIDE LAYER AND IT WILL BREAKDOWN FASTER!

  4. #4
    Join Date
    Apr 2000
    Posts
    1,303

  5. #5
    Join Date
    Sep 2003
    Location
    Western PA
    Posts
    1,358
    Printing in all CAPS has long been considered hard to read.

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