[GSBN] Window Detailing Question

John Swearingen jswearingen at skillful-means.com
Tue Nov 20 01:59:32 UTC 2012 

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
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