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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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Energy Assessment: adding u values - is my sum/method right?

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    • CommentAuthorRobinB
    • CommentTimeAug 30th 2009
     
    I want total U value of ICF wall U value 0.19 and extra 65mm PU insulation board at 0.3 . Does this look right?

    1/0.19 = .5261
    1/0.3 = 3.333

    5261
    + 3333
    = 8594

    1/8594 = combined U value of 0.116
    • CommentAuthorSaint
    • CommentTimeAug 30th 2009
     
    Robin,

    If I'm understanding you correctly:

    You have an ICF wall with a U value of 0.19W/m2K. That represents an R value of 1/0.19 = 5.262m2K/W

    65mm of PUR. Lets say PUR has a thermal conductivity of 0.025W/mK. That gives an R value of 0.065/0.025 = 2.6m2K/W

    Add the two R values together = 7.862m2K/W . So the resultant U value is 1/7.862 = 0.127W/m2K
    • CommentAuthorRobinB
    • CommentTimeAug 30th 2009
     
    Saintly!
    thanks

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