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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

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    • CommentAuthorward32
    • CommentTimeDec 14th 2014
    I have been looking for good performance windows and while my preferred supplier has provided all the test data I cannot find any air permeability reference information for comparison. The test window has a Uw of 0.7 and an air permeability of 3m^3/h m^2 (or 0.75m^3/h m) @100Pa.

    I calculate in my design I have 20m^2 of glazing to a volume of 235m^3 so the windows alone could account for 0.225ach. But this is at 100Pa, perhaps this might be half at a test pressure of 50PA!

    Can anyone point to some reference data for air permeability of windows so I can make an assessment?
    • CommentAuthorEd Davies
    • CommentTimeDec 14th 2014
    100 Pa is a strange pressure to quote. Leakage at 50 Pa might be half or it might be a bit more: leakage is proportional to pn where, for buildings, 0.5 < n < 1.0 depending on what sort of holes it has.

    What does the 0.75 m³/(h·m) figure refer to? Is it the leakage for the length of window perimeter? E.g., a 1 m × 1 m window would be 4 m × 0.75 m³/(h.m) so 3 m³/h with an area of 1 m² so 3 m³/(h·m²)?
    • CommentAuthorward32
    • CommentTimeDec 14th 2014
    I tried to upload the PDf data sheet but it doesn't work. The figure of 0.75 m³/(h·m) is on the data sheet as being equivalent to 3m^3/h m^2, but in those units.
    • CommentTimeDec 14th 2014
    Can you put a link to the pdf, assuming you downloaded it.
    • CommentAuthorward32
    • CommentTimeDec 15th 2014
    Here is one of the pages of the data sheet, no link as it was direct from the window manufacturer. It would be great if I could find similar test results from a range of suppliers! All test data is the same but for different window formats.

    Does anyone know where I could see some comparable data from different window suppliers?
    • CommentAuthorward32
    • CommentTimeDec 15th 2014
    The other pages are the same except for the last which details U values.
    • CommentAuthorward32
    • CommentTimeDec 17th 2014
    Can anyone help?
    The industry standard for classification of window air permeability is EN 12207, as in the certificate
    you’ve provided. It would typically be on a CE Declaration of Performance - (but not mandatory for the UK DoP) that every manufacturer should now be providing.

    The testing is carried out as prescribed in EN 1026.
    3m³/h m² overall window area & 0.75m³/h m opening joint length @100Pa is the maximum limit that has to be met to achieve Class 4. I would be sure that the tested window would have come in quiet a bit lower as it would be surprising not to get to Class 4 – particularly on a window that has been ‘prepared’ for such a test. On a good window the air leakage will be very close to the x-axis even at 600Pa -the actual testing involves pressure differentials of up to 600Pa. The reference air permeability for classification (comparative) purposes is 100Pa
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