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GSBN: Digest for 11/21/05



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-> Re: GSBN: More on moisture
     by Graeme North ecodesign@...
-> Re: GSBN:re: Moisture Problem (Addendum(b))
     by Paul Lacinski paul@...


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Date: 21 Nov 2005 21:31:54 -0600
From: Graeme North ecodesign@...
Subject: Re: GSBN: More on moisture

Hi John, Rene -

The air tightness thing, and lack of loose fill or voids is something that
has been hammered home to me in this latest discussion.

I'm inclined to agree with Rene that the interior plaster is often more
important than the exterior.

By the way, the one instance I have seen of condensation inside earth walled
buildings in NZ was a woman in a very cold climate who was in the habit of
closing the windows and boiling soup all winter - not helped by cement
plasters on the mud brick walls, with acrylic paint, and poor solar design
- -it this experience with earth as much as anything that makes me sure that
the hygroscopic qualities of natural (unstabilsed) earth plasters, esp. on
interior surfaces of straw walls will help immensely in keeping strawbale
walls dry.

Interesting.

Cheers,


Graeme,
Graeme North Architects,
49 Matthew Road,
RD1, Warkworth,
New Zealand 1241
Ph/fax +64 (0)9  4259305

www.ecodesign.co.nz




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Date: 21 Nov 2005 22:12:58 -0600
From: Paul Lacinski paul@...
Subject: Re: GSBN:re: Moisture Problem (Addendum(b))

Rob, Dan and all,

Sorry for my slow response.

The rafters are regular old lumber (a); 2x12's if my memory is
correct.  The poly/cellulose is retained by strapping, to which the
drywall is attached.  The ventilation space is exactly what is
created by Proper Vent-(not very permeable, thin foam tray) say, 1.5
inches?, with openings at soffit and ridge.

I should add that the ice was only on the outer 4 feet or so of the
sheathing, and that it didn't occur at all in areas of the south roof
that are over large windows with no bales above.

Also, Dan Smith said:

How are the inside joints between wall and ceiling sealed?

The answer is- not very well. A structural timber separates the wall
and ceiling planes, and  there was clearly massive air leakage at
these joints.  The joint between timber and plaster was backed with
15 lb felt, but it was not sealed in any effective way to either the
ceiling poly or the beam.  I'm pretty sure that most of the moisture
in the roof cavity came from this point, though I'll be nothing short
of thrilled if Rob can demonstrate otherwise.  Nonetheless, this
doesn't explain why the moisture level got so high throughout that
outer 30-50 mm zone of the wall, even in areas that had very little
exposure to rain, and why people are experiencing seasonal damp
patches in houses that should be well beyond the drying of their
construction moisture....

Thanks again for all of your thoughtful responses!

Paul

>Scooz 'eh  Moi;
>
>In his previous message, that dodo Stronzo di Nord forgot to ask:
>
>"Were the rafters  (a) solid lumber (or TJIs)
>                              or
>                     (b) Scissors or parallel chord trusses ?"
>
>                and
>
>"What sort of a ventilation space was provided over the insulation in the
>rafter bays of the cathedral ceiling  and what arrangement was used to
>provide exhaust capability for the ventilation space ?"
>
>=== * ===
>Rob Tom
>Kanata, Ontario, Canada
><ArchiLogic at chaffyahoo dot ca>
>(winnow the chaff  from my edress in your reply)
>
>----
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>representatives of regional straw construction organizations. The
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>
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- --
Paul M. Lacinski
Sidehill Farm
GreenSpace Collaborative
Mail: PO Box 107
Packages: 137 Beldingville Rd.
Ashfield, MA 01330 USA
+1   413 628 3800

View excerpts from Serious Straw Bale at:
<a  target="_blank" href="http://www.chelseagreen.com/2004/items/seriousstrawbale";>http://www.chelseagreen.com/2004/items/seriousstrawbale</a>


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