Cob: Intro and humidity in cool climates

[Shannon C. Dealy]

On Thu, 8 Aug 2002, yew wrote:

[snip]
> plenty of rain (30+ inches here during the 6 really humid months) and high
> humidity pretty much all season long.  A few years ago, we lived in a small,
> poorly insulated farmhouse and discovered firsthand what interior humidity can
> do.  Mold and mildew on the lower parts of the walls were a real problem,
> mostly due to our poorly ventilated bathroom shower.  While we can remedy the
> ventilation problem (for the most part), it's almost impossible to keep
> interior humidity levels low without a dehumidifier.
[snip]

>From your description, I wouldn't worry about it, you don't say exactly
where you are, but cob has been built without problems in a wide range of
climates throughout the Pacific Northwestern area of the USA, including
one in the rainforest area of of Olympic penninsula of Washington state
(120+ inches /year).  From your description, I don't think your mold and
mildew problems were due to the humidity so much as poor bathroom
ventilation and possibly even more important, poor insulation.  Poor
insulation can be much more of a problem in preventing mold and mildew
than people realize.  In winter time, the surface of poorly insulated
exterior walls are much colder than the interior of the building, and can
cause large amounts of moisture to condense before it gets the chance for
bathroom ventilation fans to draw it outside, a well insulated house in
winter will have far less of a problem with condensation on it's walls,
because the walls will have a temperature comparable to the interior air
temperature.  Aside from the thermal issue, cob is very good at
stabilizing humidity levels, and can suck up a great deal of excess
moisture without any problems, including any mositure condensing on the
surface of the walls, which should greatly reduce any problems with
mold/mildew.


Shannon C. Dealy      |               DeaTech Research Inc.
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