[GSBN] Window Detailing Question

[Brian Hodge]

Hi all,

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.



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.



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.



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.



I trust this helps someone.



Regards



Brian



*From:* GSBN-bounces at sustainablesources.com [mailto:
GSBN-bounces at sustainablesources.com] *On Behalf Of *john rehorn
*Sent:* Wednesday, 21 November 2012 9:17 AM
*To:* Global Straw Building Network
*Subject:* Re: [GSBN] Window Detailing Question



Bill,



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 ...?"



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 ..."



John Rehorn

Colorado Straw Bale Association

2012 International Straw Builders' Conference

www.strawbaleconference.com









On Nov 20, 2012, at 1:22 PM, Bill Christensen wrote:



  Hey, I've got a <sarcasm> brilliant idea:

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!

I'm sure that wouldn't create any other problems...

</sarcasm>

On 11/20/12 1:42 PM, John Straube wrote:

 Another John here.
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.
I think Bob Theis is correct that it is easier to waterproof the window on
the flat, eg on the exterior face.
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.
If the window is pulled in somewhat (say 4-6"), the head and jambs become
very protected but the sill becomes very exposed.
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.
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)



_______________________________________________
GSBN mailing list
GSBN at sustainablesources.com
http://sustainablesources.com/mailman/listinfo.cgi/GSBN
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.sustainablesources.com/pipermail/gsbn/attachments/20121122/29cb85e2/attachment.htm>