Armaflex/cell insulation

Discussion in 'Metal Boat Building' started by FreeWill, Mar 20, 2012.

  1. FreeWill
    Joined: Mar 2012
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    Location: Cambridge, UK

    FreeWill New Member

    Hi everyone.
    First post on the forum... I posted this on another thread from ages ago, but I figured I'd start my own too, as few if any will get to the end of a 10 page thread!
    I'm looking to insulate my dutch barge (steel). For various reasons its not practical to put any wood panelling over the top, and I wonder whether anyone could give me advice on whether you can paint armacell/armaflex? If so do you need a special type of paint? If so, where can I buy it?
    Can anyone recommend an armacell/flex supplier in England for a small quantity?
    In addition, I live in the south of England, could someone advise me how thick the armacell/flex will need to be to avoid condensation (for the same practical reasons I can't cover it with wood pannelling, the thinner I can get away with the better)?
    Thanks in advance,
    Will
     
  2. FreeWill
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    FreeWill New Member

    P.S. I have tried emailing the company for this info, but they haven't responded (I think they might have more important things to do!).
     
  3. MikeJohns
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    MikeJohns Senior Member

    Will
    If it is simply to prevent condensaton given the temperature gradient from inside ambient to external ambient you make sure the dewpoint is within the insulation. In reality the inside of the steel can be considered ambient outside temp so the gradient is always across the thickness of the insulation. If the insulation is a snug fit at the periphery of the cavity and close but not required to be touching the steel, so any thickness of closed cell foam will stop the condensation forming even 5 mm will do.

    We have a very cheap source of insulation availbale in Australia, it's 35mm sheets of expanded polystyrene with aluminium foil on the surfaces coloured on one face and bright reflective on the other. It's fully approved and fire retardent and when cut and fitted its looks quite servicable. We pay around $40 for a 2.4 by 1.2m sheet.
     
  4. peter1962
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    peter1962 Junior Member

    On armaflex, in this thread from 2009 you wil find a lot of usefull information. But did you search on the website for the information sheets ? It might well be that the info you are searching for is available there.

    http://www.boatdesign.net/forums/metal-boat-building/steel-hull-isolation-alternatives-foam-26839-2.html
     
  5. peter1962
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    peter1962 Junior Member

  6. ImaginaryNumber
    Joined: May 2009
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    ImaginaryNumber Imaginary Member

    Will, at this link there is a calculator to estimate the amount of insulation you need for a specified interior and exterior temperature, interior humidity, and type of insulation.

    http://www.dew-point.us/

    I left the default WALLS and STREET.

    Change the TEMPERATURE and HUMIDITY to the worst case situation you are designing for. Probably should assume that both the indoor and outdoor humidity will approach 100% at some point.

    Under MATERIAL, click in the first box and you will get a drop-down menu. I selected HEATERS HARD, then STYROFOAM. (I'm thinking the R-value of Styrofoam is about the same as Armaflex)

    Next play with the THICKNESS.

    On the graph, as long as the TEMPERATURE line and the DEW POINT line do not cross, you are okay. If they do cross the graph will inform you that you can expect condensation.

    As an aside, when you install insulation, for best results, you must seal the edges of the foam panels such that no humid interior air can reach the hull. That means it is best to either adhere the foam panels directly to the hull, or else seal the edges of the panels to each other and the bulkheads, etc, so that no interior air can reach the cold hull. If you seal some areas and not others, you may get condensate behind the foam, which cannot drain out to the bilges --- not good!
     

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  7. MikeJohns
    Joined: Aug 2004
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    MikeJohns Senior Member

    I think importantly any amount of insulation stops interior surface condensation, the dew point won't fall on the interior surface.
    The interior steelwork should be free draining to the bilge and the moisture content of the insulation and cavities is considerably less than the interior air and it quickly runs out of moisture, ie finite condensation.

    The most useful thing anyone living in a boat in cold weather can do is to reduce interior moisture. The best way is to let some of the exterior air into the boat and vent some of the interior air out. This is achieved by any heating system that draws external air in, other heating systems that only exhaust air should be provided with good vents to draw external air into the boat.
     
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