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If I were them I would not have a great deal of trust in the
architect.<br>
<br>
However, in response to Rob, <i>stachybotrys atra </i>is not the
fungal species that I would be concerned about at the design stage.
If local relative humidity gets up to the levels where <i>S.Atra</i>
can thrive, then other problems will have occurred too. And the
climate in southwest England (where I used to live) is much more
humid than that in eastern Canada where Rob's examples come from, so
humidity issues need more careful attention.<br>
<br>
The mould species to pay attention to in design are the xerophilic
primary colonisers - primarily <i>eurotium </i>spp and <i>aspergillus
</i>spp. The most xerophilic appears to be <i>aspergillus repens</i>:
at 20degC its mycelia can grow at about 75% rh - higher rh values
are required at both lower and higher temperatures; and spore
germination also requires higher rh values.<br>
<br>
My own findings - based on computer modelling - indicate that
properly-designed, properly-detailed, properly-constructed strawbale
buildings are safe from <i>aspergillus repens</i> growth in a humid
temperate maritime climate, provided that (i) relative humidity
indoors is controlled below 70%, and (ii) high vapour transmissivity
plasters and renders are used (i.e. clay and lime plasters,
preferably with no use of Portland cement whatsoever). I think that
most (maybe all) experienced sb builders in that climate zone in
Europe would confirm this from practical experience.<br>
<br>
Mark<br>
<br>
<br>
<br>
On 2011:03:25 12:44, RT wrote:
<blockquote cite="mid:op.vswwzm2h4f5a3n@owner-b0bdc4ac6" type="cite">On
Thu, 24 Mar 2011 13:00:02 -0400,
<a class="moz-txt-link-rfc2396E" href="mailto:gsbn-request@greenbuilder.com"><gsbn-request@greenbuilder.com></a> wrote:
<br>
<blockquote type="cite">Date: Thu, 24 Mar 2011 07:56:02 -0400
<br>
From: carolatkn
<br>
Subject: [GSBN] Mycotoxins
<br>
</blockquote>
<br>
<blockquote type="cite">
<br>
I recently met a young couple wanting to build a new home on
their family farm in south west England. They had been told by
their architect that they should discount straw bale immediately
as they would be certain to die from exposure to mycotoxins!
<br>
</blockquote>
<br>
<blockquote type="cite">My initial response is that if the straw
is baled and kept dry there will be few moulds anyway and crack
free plaster would prevent any that were present making their
way into the living space.
<br>
</blockquote>
<br>
[BIG <snip>]
<br>
for full text of message and thread see:
<br>
<a class="moz-txt-link-freetext" href="http://greenbuilder.com/pipermail/gsbn/2011q1/001379.html">http://greenbuilder.com/pipermail/gsbn/2011q1/001379.html</a>
<br>
<br>
Sometime within the past 10 years (+/-) the City of Gatineau (in
the Province of Quebec, Canada (just across the river from Ottawa
of which the former City of Kanata is now a part)), wanted to
enact a by-law to ban the use of straw bales for making buildings
in that city.
<br>
<br>
The City's reason for wanting to do so was because of
moisture-related problems with at least one SB house (a two-storey
dwelling, exterior plaster fully exposed to rain wetting) in that
city.
<br>
<br>
A woman who spent time in that house and another SB large building
(with known wet SB issues) elsewhere in the province of Quebec
reported that the buildings made her sick.
<br>
<br>
Don Fugler was one who kept files on these before he retired from
CMHC. I don't know if Don was able to acquire any funding to have
forensic testing done on the affected buildings as he did for the
report:
<br>
<br>
"Pilot Study of Moisture Control in Stuccoed Straw Bale Walls"
(June 1997)
<br>
<br>
where the walls and floors of SB buildings that had been occupied
for ~10 years were cut into, straw samples taken/inspected and
moisture paths identified.
<br>
<br>
That report, which includes nice colour photographs of
mould-deteriorated straw should still be available from CMHC.
<a class="moz-txt-link-freetext" href="http://cmhc.ca/">http://cmhc.ca/</a>
<br>
<br>
If not, I'd consider scanning it and putting it into a PDF if
sufficient demand warrants (and if CMHC gives its permission).
<br>
<br>
As with any other moisture-susceptible cellulosic material that is
allowed to get wet and not provided with the means to dry
properly, one can expect microbial activity to occur.
<br>
<br>
It was mentioned by a senior bureaucrat at Health Canada (at least
15 years ago) that straw is an ideal host for Stachybotrys atra
(Stachybotrys chartarum) , a black mould that was a prime suspect
in infant deaths ( pulmonary hemorrhaging).
<br>
<br>
True, SA needs humidity levels of ~90% in order to develop but
that would not be out of the question in a SBH built in a Cold
Climate region where insufficient attention was paid to
air-sealing and/or keeping rain off of exterior plaster and/or
faulty flashing details and/or about a half dozen other reasons.
<br>
<br>
Bottom line: The fears expressed by the Brit architect may be
over-stated but not completely off-base, probably a hysteria borne
of seeing bits and pieces of messages like this one, out of
context.
<br>
<br>
<br>
</blockquote>
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