[GSBN] Window Detailing Question
John Swearingen
jswearingen at skillful-means.com
Mon Nov 26 23:41:38 UTC 2012
John,
Although on paper (or with paper) mounting the window to the outside is
easier, exposed vertical breaks in the plaster are still the most
vulnerable issues for a bale wall, because there isn't a layer of building
paper to flash behind. My thought is that moving the window inside the
bale wall means that any water traveling down behind the stucco must make a
90 degree turn, from vertical to horizontal, which allows the opportunity
to intercept easily on the horizontal plane, with flashing, before it gets
to the window. To me this seems easier to protect than a direct vertical
joint.
What do you think? I can't stand to think that Bob might be right about
this!
John
On Tue, Nov 20, 2012 at 11:42 AM, John Straube <jfstraube at gmail.com> 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)
>
>
> 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 project coming in and we're thinking in terms of
>> some
>> passive haus - kinda design concerns as 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
>> the thickness of the wall, as opposed to how we normally set them at
>> the exterior edge
>> of the wall. The idea is that we will provide more thermal resistance
>> through the wall at
>> the jamb, head, and sill in order to transfer through more fiber rather
>> than just being
>> able to nip diagonally through 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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>
>
> --
> 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
>
>
> _______________________________________________
> GSBN mailing listGSBN at sustainablesources.comhttp://sustainablesources.com/mailman/listinfo.cgi/GSBN
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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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