[GSBN] Window Detailing Question
nature boy
moontrout at yahoo.com
Tue Nov 20 20:30:47 UTC 2012
Wow, thanks for all of the knowledge, experience, and passion
that a single question reveals in this group! There surely isn't one
simple answer, and our own questions are apparently questionable!
Okay then, we'll sort through all of this feedback and figure out what
will work best in this case.
Have a lovely holiday everyone!
Mark
Mark Lakeman
Co-Founder Principal & Design Lead
The City Repair Project communitecture, inc.
Portland, Oregon Architecture & Planning
503-381-5885 503-230-1293
www.cityrepair.org www.communitecture.net
________________________________
From: John Straube <jfstraube at gmail.com>
To: Global Straw Building Network <GSBN at sustainablesources.com>
Cc: John Swearingen <jswearingen at skillful-means.com>; nature boy <moontrout at yahoo.com>; Patrick Donaldson <Patrick at communitecture.net>
Sent: Tuesday, November 20, 2012 11:42 AM
Subject: Re: [GSBN] Window Detailing Question
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)
Dr John Straube, P.Eng.
www.BuildingScience.com
On 12-11-19 8:59 PM, John Swearingen wrote:
Ah, finally you are coming around to moving the windows inward, though I would challenge your reasoning. There are many good reasons to place the windows in mid-wall, but I don't think preventing thermal gaps is one of them; the difference is likely to be minor compared to other issues.
>
>
>Here are a few:
>
>
> 1. Shading: by far the most significant thermal effect of window placement is the degree of shading provided, especially on E & W orientations.
>
> 2. Rain cover: The technical problem with bale walls is that windows are placed in a wall that has no sheet membrane to lap over the windows. This problem exists wherever the window is located, but when water sheeting down the wall has to make a 90 degree turn, from vertical to horizontal, there are more opportunities to intercept and disperse water before it gets past the window. (Bob Theis likes the windows pasted to the outside in order to avoid the 3D waterproofing issue, I think it's foolish to think that it's really any easier).
> 3. Sill detailing: Wider sills provide better dispersion of rain striking the window location. (However, wind-driven rain can accumulate)..
> 4. They look awesome: show off how thick your walls really are.
> 5. They look friendly: shallower sills on the interior are generally more pleasing and less like a monk's cell or dungeon (take your pick).
>My thought....
>
>
>John
>
>
>
>
>
>
>
>On Mon, Nov 19, 2012 at 5:25 PM, nature boy <moontrout at yahoo.com> wrote:
>
>Hi Folks,
>>
>>
>>Mark Lakeman at communitecture and City Repair in Portland here.
>>
>>We have a new bale projectcoming in and we're thinking in terms of some
>>
>>passive haus - kinda design concernsas well. Can anyone please comment
>>
>>on the question below,please?
>>
>>
>>- So, we're thinking of bringing the windows of this building inboard to the middle of
>>
>>thethickness of the wall, as opposed to how we normally set them at the exterior edge
>>
>>of thewall. The idea is that we will provide more thermal resistance throughthe wall at
>>
>>the jamb, head, and sill in order to transfer through more fiber rather than just being
>>
>>able to nip diagonallythrough the wall around the window frames.
>>
>>
>>Is it worth doing this in consideration of potentially increased water infiltration issues?
>>Please advise!
>>
>>
>>Thanks always,
>>
>>Mark
>>
>>
>>
>>Mark Lakeman
>>
>>Co-Founder Principal & Design Lead
>>The City Repair Project communitecture, inc.
>>Portland, Oregon Architecture & Planning
>>503-381-5885 503-230-1293
>>www.cityrepair.org www.communitecture.net
>>
>>
>>
>>
>>
>>________________________________
>> From: Chris Magwood <chris at endeavourcentre.org>
>>To: Global Straw Building Network <GSBN at sustainablesources.com>
>>Sent: Tuesday, November 13, 2012 4:13 AM
>>Subject: [GSBN] Can bale buildings be air tight?
>>
>>Hi all!
>>
>>Maybe the question of whether or not a bale building
can be built air tight hasn't been keeping you all
awake at night, but it's caused Jen and I some long
evenings of thought and lots of detail drawings on
our plans! Maybe that's just what keeps northerners
warm at night...
>>
>>We've been honing in on good results over the past
couple of years, and this year we finally nailed it
(but didn't put a nail through it... that would have
been counter-productive). We just did a blower door
test on our most recent project and ended up with a
result of 0.99 ACH50. That's approaching the
PassiveHaus goal of 0.6, and we realized after the
test that we hadn't covered up the open sump pit in
the basement, so we may actually get to PH levels
with the final test.
>>
>>The building has a mix of site-built, clay plastered
walls and prefabricated, lime/cement plastered
walls. We've long used a system that uses a flexible
air barrier (house-wrap type membrane) at the edges
of the walls where the plaster will meet ceiling,
floor and intersecting walls. The membrane wraps
down behind the plaster by 3-4 inches. What was
interesting with this building was to find that in
some areas that detail worked very well, and in
others it didn't help much at all.
>>
>>What this tells us is that unprotected plastered
edges leak... a lot! Our first blower test helped us
discover that some of these seams were leaky. One
leaky wall accounted for a shocking 74 square inches
of leakage! By eye, it just looked like the usual
plaster shrinkage around the edge of the wall, maybe
1/8 inch. But multiply that around an entire home
and it's no wonder that many bale buildings under
perform in blower door tests. You can see photos of
these areas on our project blog at http://endeavourcentre.org/2012/11/blower-door-test-1/
>>
>>What we don't know is why some areas stayed tight
and others didn't. Our best guess is that it can
come down to quality of work. How long was the
barrier tail left? How well was the mesh installed
over it? How vigorously was the plaster pushed into
the mesh? The plaster pulling away at the edge as it
shrinks also seems to cause some slight bending of
the skin inward, taking it away from the barrier.
>>
>>One good take-away from this project is about the
beauty of clay plasters. The leaky edges of the clay
plastered walls were relatively easy to address...
moisten the edges a bit and squeeze in more clay
mix. Everything bonds together and the seams went
from very leaky to completely tight!
>>
>>Now, if anybody happens to ask if them there bale
houses can be air tight, it's possible to answer
yes.
>>
>>Cheers,
>>
>>Chris
>>
>>-- Chris Magwood
>>Director, Endeavour Centre
>>www.endeavourcentre.org
>>
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>>
>>
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>>
>
>
>
>
--
>John Swearingen
>Skillful Means Design & Construction
>2550 9th Street Suite 209A
>Berkeley, CA 94710
>510.849.1800 phone
>510.849.1900 fax
>
>Web Site: http://www.skillful-means.com
>Blog: https://skillfulmeansdesign.wordpress.com
>
>
>
>_______________________________________________
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