thermal bridging around windows with wrap around external insulation

[fostertom]

Going back over this with great interest, but slightly thrown by what may be a misprint:

by limiting the Ug to 0.7 it helps to ensure that the manufacturer does not place undue emphasis on the design of the frame

If you confirm Mark that that should read 'design of the glass', then I'm happy, otherwise baffled!

The attached is what we're talking about?

I also had a question in my previous post on this thread, previous page.

[Mark Siddall]

Tom,
I stand by what I said.
In a central European climate if the 0.7 U-value criteria was not stated by PHI then a manufacturer may improve the frame but may fail to address down draft risks (which are dominated by Ug not Uf.)

Mark

[fostertom]

If a manuf cd use glass of Ug better than 0.7 (which wd be gd against downdraughts) he's allowed no credit for that, so has no alternative but to improve the frame instead, and may as well use cheaper, downdraughty glass no better than 0.7.

[Mark Siddall]

Tom,
0.7 is NOT "down drafty" all comfort criteria are satisfied.
No such things as "credits" with PH. Perform or don't perform..... Of course we are talking about PasivHaus Certified windows.
Uncertified windows can be used in a PH.... but the min Ug of 0.7W/m2K and Uw of 0.8W/m2k (and min g of 0.5) would still apply for energy performance and comfort issues.

Certified system is not perfect but does allow easy comparison within the market place (otherwise the specifier has to become a glazing boffin.....)

Mark

[fostertom]

I'm none the wiser, will ask again on another occasion.