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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Hi all,</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Some time back we began enveloping the window buck in render/cob
so that the buck is completely covered and sealed. The window is then
fixed in position with the use of expanding foam. The expanding foam is a
mechanical connection which also provides insulation and a water proof seal. By
doing this there is no entry point for water , which normally happens around
the junction of the timber to render. We complete the second coat of render
before fitting the windows, which also assists in the drying of the second coat
inside due to the increased air flow by not having the windows in place. </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">The expanding foam needs a dust free surface to adhere to, so we
treat the surface of the render in alignment with the window with 10 parts
water to 1 part bondcrete, which stabilizes the render. We have now been using
this method of window installation for about 6 years and even in high wind
applications we have never had cracking around windows or any water leaks.
Obviously in order to do this you must allow a significant amount of clearance
between the buck and the window to allow for the cob & render. We allow
100mm in the width and 60 in the height.</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">The foam must be overfilled so that the excess foam can be cut
of broken off as this gives a surface that the render will adhere to, where-as
the natural finish is too smooth. Once the window is held in place with the
expanding foam, we use cob around the window to generate the final shape
required, which also provides a very strong structure around the window.</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">This method of construction is obviously of no value to people
unwilling to use expanding foam, but it has served us well, and completely
solved the problem of leaks around the windows.</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">I trust this helps someone.</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Regards</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Brian</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
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<div style="border:none;border-top:solid #b5c4df 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">
<a href="mailto:GSBN-bounces@sustainablesources.com">GSBN-bounces@sustainablesources.com</a>
[mailto:<a href="mailto:GSBN-bounces@sustainablesources.com">GSBN-bounces@sustainablesources.com</a>] <b>On Behalf Of </b>john rehorn<br>
<b>Sent:</b> Wednesday, 21 November 2012 9:17 AM<br>
<b>To:</b> Global Straw Building Network<br>
<b>Subject:</b> Re: [GSBN] Window Detailing Question</span></p>
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<p class="MsoNormal"> </p>
<p class="MsoNormal">Bill,</p>
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<p class="MsoNormal">It's ideas like that from which innovation springs.
You're right, there are always unintended consequences to everything, but
I've learned the most from the projects I've been involved in when someone
asked "Why ...?" or Why not ...?" </p>
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<p class="MsoNormal">Just think of the time someone said, "I've got a
brilliant idea: Instead of cutting sods and stacking them into walls to
make a dugout home, let's grow the prairie grass real tall and use that new
fangled baler doohickey to make building blocks out of grass ..."</p>
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<p class="MsoNormal">John Rehorn</p>
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<p class="MsoNormal"><span style="font-size:13.5pt;font-family:"Helvetica","sans-serif";color:black">Colorado Straw Bale Association</span></p>
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<p class="MsoNormal"><span style="font-size:13.5pt;font-family:"Helvetica","sans-serif";color:black">2012 International Straw Builders' Conference</span></p>
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<p class="MsoNormal"><span style="font-size:13.5pt;font-family:"Helvetica","sans-serif";color:black"><a href="http://www.strawbaleconference.com">www.strawbaleconference.com</a></span></p>
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<p class="MsoNormal"><span style="font-size:13.5pt;font-family:"Helvetica","sans-serif";color:black"> </span></p>
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<p class="MsoNormal"><span style="font-size:13.5pt;font-family:"Helvetica","sans-serif";color:black"> </span></p>
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<p class="MsoNormal">On Nov 20, 2012, at 1:22 PM, Bill Christensen wrote:</p>
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<br>
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<p class="MsoNormal">Hey, I've got a <sarcasm> brilliant idea:<br>
<br>
Put the top in 4-6" to protect the head and jambs, as John Straube
suggests. Then put the bottom of the window flush with the exterior, so
you don't have to deal with sills! <br>
<br>
I'm sure that wouldn't create any other problems...<br>
<br>
</sarcasm><br>
<br>
On 11/20/12 1:42 PM, John Straube wrote:</p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><span style="font-family:"Helvetica","sans-serif"">Another
John here.<br>
Provided the window frame is within the lines of the exterior and interior
surfaces of the strawbale wall, locating the window has almost zero impact on
thermal performance. Perhaps 3-5% for the extreme positions and less than
that when you are even a few inches in.<br>
I think Bob Theis is correct that it is easier to waterproof the window on the
flat, eg on the exterior face. <br>
However, I know that locating the window on the face exposes it to MUCH more
rain water, and so I NEED to get better water proofing.<br>
If the window is pulled in somewhat (say 4-6"), the head and jambs become
very protected but the sill becomes very exposed. <br>
So to get any advantage we need to detail the sill carefully (pesky
corners). But, steeply sloping (say 6:12) sills will also greatly reduce
risk.<br>
The bottom corners at the sill can be easily solved (in my humble opinion) by
using preformed corners, made of rubber, plastic or galv metal (check out
people like Dow and Cosella Doerken for plastic and rubber cheap corners, get
you sheet metal guy to build metal ones)</span></p>
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</blockquote>
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