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John,<br>
the thermal bridge values are per unit length of window, so it
adds up, and can be a large % of the total annual demand. The sills
usually have higher values than the sides & top which are easier
to insulate over.<br>
<br>
Yes, German (European, Passive House, etc.) windows need rough
opening space too, and it should be insulated, preferably with foam.
They differ in having a sill that attaches to the frame with a drip
on the cladding. The windows are also flashed on the sides and tops,
not clear from the drawings.<br>
<br>
I agree that sacrificing some energy efficiency for durability
is a good idea if needed. Windows & doors should have sloped
sills with pan flashing, and allowed to drain out. <br>
<br>
I just got word that I passed my Certified Passive House
Consultant test (for the 2nd time, fallout from PHIUS)<br>
<br>
<br>
<br>
On 1/29/2012 5:55 PM, John Straube wrote:
<blockquote cite="mid:4F25F88D.10605@gmail.com" type="cite">
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<font face="Helvetica, Arial, sans-serif">Bonjour mon ami<br>
<br>
I have the PHPP 2007. It shows some drawings on Page 71, but
does not show the impact of moving the window inward or outward.
It does show a wood frame wall and the fact that this has one of
the lowest thermal flanking loss (0.01 W/mK) as shown of the
four examples. It also shows a window installation that would
result in serious rot and damage when the window leaks (windows
have a high likelihood of leaking), but I suppose that is not an
energy issue ;)<br>
<br>
The Chisnall pdf shows a great example of the impact of being
really stupid, that is, putting the window in the masonry part
of the wall, and have all the insulation outboard of that. OK,
this is a big mistake, and has nothing to do with being in the
center of the wall or the center of the insulation. It is a
major problem caused by the window being installed in the
uninsulated part of the wall. Ironically, this powerpoint also
seems to show this error being committed in the photo on page
16.<br>
<br>
That one image from the passive house pdf is the close to the
answering the question, although the detail is extreme: the
window is again pushed as far out as possible, has a lot of
solid wood around it and does not actual have insulation around
it (like most windows are installed here).<br>
<br>
The passidia shows that the difference between mounting in
middle and flush to exterior is merely 0.001 W/m K. That is
very very small. Only when you install the window in the masonry
(completely missing the insulation layer) does the thermal
bridge value increase to 0.204 (obviously stupid).<br>
<br>
So again, I dont see any definitive answer that the window needs
to be installed in the middle of the wall or the middle of the
insulation (however that is defined anyway). I also have no
definitive answer (which is why I asked) but in the range of
reasonable installations, the impact seems seems to be small or
even non-existent (by small I mean <0.03 or so W/mK). Of
course, the window needs to be installed with the insulation
layer, and it should ideally be surrounded by some insulation in
the rough opening. Many of the PH drawings are unbuildable, as
they show no rough opening (I have worked in Europe and I know
that the window rough openings are sized larger than the window
to allow for installation, just like they are in north America).<br>
<br>
</font>
<pre class="moz-signature" cols="0">Dr John Straube, P.Eng.
<a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="http://www.BuildingScience.com">www.BuildingScience.com</a></pre>
<br>
On 12-01-29 12:19 PM, John Daglish wrote:
<blockquote cite="mid:92732805.20120129181909@free.fr" type="cite">
<pre wrap="">Bonjour John,
Sorry not to get back sooner, have been busy.
They calculate the installed value of the thermal bridge heat loss
coefficient W/m.K.
If you look at page 71 of the PPHPP assive House Planning Package 2007 booklet it
shows some best practices for exterieur insulation, concrete form
block, timber I beam, timber frame.
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://www.can.uk.net/conference_2011/leicester/downloads/peter_chisnall.pdf">http://www.can.uk.net/conference_2011/leicester/downloads/peter_chisnall.pdf</a>
p27 cavity wall insulation 0.11 0.01 or 0.12 W/m.K ext mid int
p28-29 external wall insulation 0.08 or 1.84 W/m.K "mid" int
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://gse.cat.org.uk/downloads/passive_house.pdf">http://gse.cat.org.uk/downloads/passive_house.pdf</a>
p9-10
There is a more complete explanation on the web site <a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://passipedia.passiv.de/passipedia_en/start">http://passipedia.passiv.de/passipedia_en/start</a>
but it is behind a "pay" wall ie. you have to become a member.
but not in German it seems :
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://passipedia.passiv.de/passipedia_de/planung/waermeschutz/fenster/fenstereinbau">http://passipedia.passiv.de/passipedia_de/planung/waermeschutz/fenster/fenstereinbau</a>
external wall insulation ETICS
0.18 or 0.017 or 1.22 W/m.K ext mid int
0.86 or 0.84 or 1.22 W/m2.K window installed U value
PS angle bracket fixings to place the window in an ETICS wall should
have thermal insulating shims!! Even the cavity wall brick fixings
fabricants are doing this now.
Cordialement
</pre>
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<div class="moz-signature">-- <br>
George J. Nesbitt, Environmental Design / Build, Building
Performance Contractor
HERS I Verifier & HERS II Rater, GreenPoint Rater new &
existing SF & MF, CABEC CEPE (Certified Energy Plans
Examiner), Certified Passive House Consultant, BPI Multifamily
Analyst, <a class="moz-txt-link-abbreviated" href="http://www.houseisasystem.com">www.houseisasystem.com</a>, (510) 655-8532 office, (510)
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