[GSBN] Window Detailing Question

Tue Nov 20 02:59:23 UTC 2012

Mark and John

I would have thought that a good way of looking at detailing is - if it
works - you don't have to fix it.

Rain driven rain is and will always be a problem - and it seems that the
strawbale community has found (?) a solution.

I like being in a monk's cell !

Bohdan ( not a monk)

From: GSBN-bounces at sustainablesources.com
[mailto:GSBN-bounces at sustainablesources.com] On Behalf Of John Swearingen
Sent: Tuesday, 20 November 2012 12:30 PM
To: nature boy; Global Straw Building Network
Cc: Patrick Donaldson
Subject: Re: [GSBN] Window Detailing Question

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 <http://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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