[Cob] Moisture, mold, and walls

[GlobalCirclenet]

Thanks for very well informed clarification. However, please note I used
the words "properly sealed" and "where it should be sealed" rather than
100% tightly sealed. "Properly sealed" still leaves moisture an escape
route, as you explained. 

paul at largocreekfarms.com
http://herbfarmer.net
*********** REPLY SEPARATOR  ***********

On 7/25/2004 at 11:54 AM Shannon C. Dealy wrote:

>On Sun, 25 Jul 2004, GlobalCirclenet wrote:
>
>[snip]
>> mold problem it's because the house isn't properly sealed against
>moisture
>> where it should be sealed, and you have to move out. Then it costs a
>[snip]
>
>This isn't correct, while a lack of seal against moisture could cause mold
>problems, it is in fact buildings that are to tightly sealed which are the
>ones making it into the news and are the source of the reports on "sick
>building syndrome".  I have looked at the facts surrounding quite a few of
>these, and in each case, the wall system sealed the house so tightly that
>moisture could not escape, and since living is an inherently moisture
>producing activity, moisture levels shot up in variouss places in the
>walls and interiors of these buildings, ultimately reaching the point
>which would support mold growth.  Cracks in interior plasters on bales
>isn't going to create a mold problem in and of itself (though in wet
>climates exterior cracks could), it also requires a source of sufficient
>moisture concentrating in that area, so cracks in a bale plaster job in a
>bathroom is far more of a concern than plaster cracks in a living room.
>The problem is not that moisture gets into walls, regardless of what
>they are made of (bales, cob, wood frame, concrete, steel, etc.), IT WILL,
>the problem is does the wall system allow the moisture to escape from any
>and all areas on average as fast as it infiltrates.  It is important to
>note here that by escape, I mean pass through the wall, since it must be
>able to reach the side of the wall with lower humidity, or it hasn't
>escaped.  Cracks in interior plasters on bale walls allow more direct
>contact with the interior air of the building, but this is a relatively
>minor issue unless that air has extremely high relative humidity (such as
>a bathroom or possibly kitchen), in which case, even a straight earthen
>plaster over the wall may have issues as well, and may not be sufficient
>to protect the bales behind them.  Moisture is going to get into the wall
>through even a perfect plaster job, it is even going to condense in the
>wall (bales or otherwise), but as long as it is able to migrate out
>reasonably quickly by wicking, air migration, or other means, mold is not
>going to be a problem.
>
>How moisture gets into and out of walls is one of the most important
>lessons of modern building, because a large percentage of building
>officials, architects, and building material manufacturers do not
>understand this most basic of problems, and in the interest of higher
>insulation / energy efficiency, reduced maintenance, etc., make the
>absolutely worst possible design choices.  Some of them have learned from
>these mistakes (based in the recent increase in articles regarding
>moisture and wall breathability), many are still clueless.
>
>[snip]
>> will mold faster than wood. Cob or other earthen material will not mold.
>[snip]
>
>It might be more correct to say that the interior of cob or earthen
>materials will not mold (where the interior of straw bales definitely
>will mold), the straw sticking out of cob as well as the organic matter in
>the soil the cob was made with will mold on it's surface, even after the
>cob has dried if the relative humidity is high enough (and yes, I do know
>from personal experience -- I sometimes wonder if I don't experiment far
>to much :-)  Mold will actually grow on anything, since even the dust in
>the air has sufficient organic matter to support mold, all it has to do is
>settle somewhere moist, this is how galvanized steel ducting in houses and
>office building is able to support the growth of mold.
>
>
>Shannon C. Dealy      |               DeaTech Research Inc.
>dealy at deatech.com     |          - Custom Software Development -
>                      |    Embedded Systems, Real-time, Device Drivers
>Phone: (800) 467-5820 | Networking, Scientific & Engineering Applications
>   or: (541) 929-4089 |                  www.deatech.com
>
>
>
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