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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    • CommentAuthorMike1
    • CommentTimeOct 9th 2017
     
    Lots of good technical reasons given above - it's clearly the way to go, if you can afford it.

    I remember having very similar conversations 30 years ago with clients who weren't convinced that it was worth paying the extra for double glazing compared to single glazing...
    •  
      CommentAuthordjh
    • CommentTimeOct 9th 2017
     
    Posted By: TimSmall
    To be fair, they aren't saying that it's a ph certified component, just that its U value meets the ph standard (with the implication being for cool-temperate).

    Exactly. But since unless the U-value is measured to the PH standard, it probably doesn't meet it (check the definitions for U-value measurement to various standards if you're not clear), it's extremely likely to be greenwash. Hence my doubts about their claims.
    • CommentAuthordelprado
    • CommentTimeOct 11th 2017
     
    I have made enquiries with Residence 9 and apparently it is calculated by an independent BFRC registered simulator who are regularly audited by the BFRC. Is that worth anything? I wish I could share the report with you djh, care you share your email? I'd appreciate any advice :)
    • CommentAuthorDarylP
    • CommentTimeOct 11th 2017
     
    The U-value for a window should be that for the whole window opening, including the window frame.
    Measurements of thermal transmittance in the case of doors and windows should be made according to
    BS EN ISO 12567-1.
    Alternatively, U-values of windows and doors may be calculated using BS EN ISO 10077-1 or BS EN ISO 10077-2.

    .... from SAP 2012, for UK Building Regs.
    •  
      CommentAuthordjh
    • CommentTimeOct 11th 2017
     
    There's a fair summary of the differences between UK standards and the PHI approach in
    https://www.aecb.net/wp-content/plugins/aecb-publication-library/librarian.php?id=8523&file=8516
    •  
      CommentAuthorfostertom
    • CommentTimeOct 11th 2017
     
    Posted By: DarylPThe U-value for a window should be that for the whole window opening, including the window frame
    Not the opening, just the glass and frame. The opening is beyond control of the window manuf, is a matter of architecural detailing.
    • CommentAuthorTimSmall
    • CommentTimeOct 30th 2017
     
    I thought (BICBW) that the U value given in BFRC calculations was using EN 10077 (like PHI use), but unlike PHI methods:

    BFRC makes no allowance for thermal bridging due to installation (this will tend to lower the BFRC U-value vs. the PHI U value).

    BFRC use a smaller standard window dimension that is used by the PHI as standard (this will tend to raise the BFRC U-value vs. the PHI U value - since for triple glazing assuming the frame U value is higher than the glazing U value - which it nearly always is).

    BFRC doesn't mandate a particular spacer + glazing combo (you can now quite easily do better than the PHI standard glazing+spacer combo with many frame systems, so this will lower the BFRC U value if the frame allows for a sufficiently thick glazing unit).

    PHI also specify a minimum surface temperature for certified windows I think?

    I believe (BICBW again), so please say if that's correct, that if you use non-certified windows, then you just have to meet:


    Uw(installed) <= 0.85 W/m²·K

    (for cool temperate climate zones) I think? I don't think there is a minimum requirement for lowest temperature point on the frame?

    So:

    There are clearly differences between a "window which is suitable for [cool temperate climate] passivhauses", and a "Passivhaus Institute certified window" (with the former being a superset of the latter), and:

    You don't have to use PHI certified windows in a certified passivhaus (but it's generally less hassle if you do).


    ... but if you can build a window from that profile and install it in a certified Passivhaus, then I don't think it's unreasonable to make that claim in your advertising materials.
    •  
      CommentAuthordjh
    • CommentTimeOct 30th 2017 edited
     
    Posted By: TimSmallI thought (BICBW) that the U value given in BFRC calculations was using EN 10077 (like PHI use)

    BFRC can calculate U-value using EN 10077 but they also allow another method as DarylP said.

    PHI also specify a minimum surface temperature for certified windows I think?

    Yes, the temperature difference from the internal temperature must be less than 3°C.

    I don't think there is a minimum requirement for lowest temperature point on the frame?

    I believe that is what the 3°C requirement is about, although I think a very limited area in the corner of windows can exceed that but don't remember exactly.

    but if you can build a window from that profile and install it in a certified Passivhaus, then I don't think it's unreasonable to make that claim in your advertising materials.

    I think it is reasonable to make that claim - that one could build a certified Passivhaus dwelling using those windows - but not to claim that the windows are Passivhaus Standard.

    Passivhaus is fairly flexible in many ways. It allows compensation of some poorer performing areas by improving the performance of other areas, as long as the overall criteria and specific performance criteria are met. You can even build a certified Passivhaus dwelling using straw bales :bigsmile:
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