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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    • CommentAuthorgoodevans
    • CommentTimeApr 16th 2017 edited
    Since looking at the 3 years of moisture data from the user lineweight on this forum - I've been a little obsessed with trying to get a handle on how moisture actually moves in/out/through/around the fabric of buildings. As a result I came across this document which others here my find interesting.


    Largely there is not very much quality data that is both publicly and freely available - however this document from: "VTT Technical Research Centre of Finland" appears to be in the public domain (but copyright). My impression is that it is a good bit of research and of interest to anyone that wishes to compare OSB with Ply.

    Where this research differs from many others is that the same set of ply and OSB samples undergo several types of test of interest to the suitability of the material for use in buildings so that a more holistic view of the various merits of OSB and ply can be made. I found it an interesting read. Enjoy.
    • CommentAuthorlineweight
    • CommentTimeApr 19th 2017
    Good to have as a reference - thanks.
    • CommentTimeApr 19th 2017
    I still have to read it properly but looks invaluable, unique even. Thanks.
    Wish they'd give trade name/brands, tho they make the point that there's much variation between samples even within same brand.
    • CommentTimeApr 19th 2017
    It's also quite old now, so product details are probably not as relevant as they might once have been.
    • CommentTimeApr 19th 2017
    Still, before more careful study, looks like OSB is a gd air barrier, contrary to persistent doubts
    • CommentTimeApr 19th 2017 edited
    Starting to dig into it.

    First question, in this early (2005) report - anyone any idea what the standard ratings Ply EU, Ply EU2, OSB, OSB EU, OSB EU2, Ply CAN, OSB CAN are equiv to? I can find no refs to these ratings. Maybe EU2 e.g. means OSB2 (as defined in a EN standard).

    Reference to wax coatings and/or wax interior-mix in OSB - news to me, and a bit liable to variation in manufacture and even more, degradation in use esp as surface coating, affecting both air- and vapour-permeability.

    All assumed glued together with varios formaldehyde-based glues. So what's the story with Irish 'zero added formaldehyde' Smartply OSB, compared say with its only UK+IRL competitor Scottish Sterlingboard, which makes no such claim? Are Irish trees so full of natural formaldehyde 'glues' that no extra is needed - but the formaldehyde content end result may be same?

    "All the tested products have very small air permeability factor and they are all quite suitable for the use as a wind barrier in conventional wall structures. The maximum measured value was about 1/3 of the recommended maximum level in Finland." Even for very thin OSB (8.4mm); indeed the difference between the only direct thickness comparison, 12.6 vs 15.5 is negligible.
    It's not so clear about hopefully plentiful vapour permeability.
    • CommentAuthorEd Davies
    • CommentTimeApr 19th 2017
    Posted By: fostertomanyone any idea what the standard ratings Ply EU, Ply EU2, OSB, OSB EU, OSB EU2, Ply CAN, OSB CAN are equiv to?
    Only read the first few pages so far but aren't those the names they give to the samples they're working with, rather than standards?

    Posted By: fostertomReference to wax coatings and/or wax interior-mix in OSB - news to me,
    News to me, too, but some sort of coating is not at all a surprise:

    • CommentAuthorgoodevans
    • CommentTimeApr 20th 2017
    That Finnish standard referred to in the document at 1.0E-5 m3/(Pa.s.m2) is not so good - assuming air permeability is proportional with pressure difference it represents an equivalent air test value of 1.8 m3/(h.m2) @ 50 Pa.

    It isn't clear from the text at what pressure the air permeability test was done at - (0 to to 2000 Pa).

    However the best Avg OSB result of 516E-9 m3/(Pa.s.m2) gives an equivalent air test result of less than 0.1 m3/(h.m2) @ 50 Pa. giving some leeway for gaps between the panels.

    (the relevant reference for Finnish air barrier value is here: http://www.ym.fi/download/noname/%7BA818E62D-9AC3-411C-9CE5-BBEC75BDF9F4%7D/124727 section 3.3) the test method used for air permeability (EN 29053:1993) is developed for acoustic properties - but of course us ordinary mortals can't see what the test method is unless we pay.
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