Cob: Re: Insulation

[Sarah Kopp]

Hi Russel,

I am prejudiced towards strawbales for their insulative value, also the
ability to build up a really thick wall quickly (I think thick is
beautiful!)  But am attracted to cob also for it's sculptural potential etc,
as you are.  I am building a strawbale house and my interior walls are wood
frame and sheetrock due to time and money constraints, but in my mind the
perfect house would be exterior walls of straw with earth plaster inside and
out, a coat of lime plaster on the exterior, and interior walls of adobe and
cob.  That way we would get all the insulating value of the strawbales, plus
the thermal mass properties of earth inside, where it counts, and the
partition walls would have the same curvy handmade quality of the exterior
walls.

The earth plastered strawbales are also very sculptural in quality - there
are no really straight or square looking walls in my house (except the
partitions, of course.)  I sculpted small and large niches into a few walls,
it is easy to do with straw.  My kitchen's exterior wall is built out in a
bay shape but could just as easily have been curved. If you use a really
high content of chaff or even 4-6 cms lengths of straw in your earth
plaster, you can sculpt even very thick details on the wall surface - like
built up door and window framing or even bas relief pictures on the walls.
I am under a lot of time constraints and have not done this (yet!) on my
house but my small experience with the earth plaster shows it is definitely
possible.

I would guess that in Manitoba you want the insulation and you can still do
a lot of creative personalizing of your house with the wall surfaces and
partition walls.

Sarah
Tsfat, Israel
-----Original Message-----
From: Russel Johnsen <wpgweb at yahoo.com>
To: coblist at deatech.com <coblist at deatech.com>
Date: ë"â àá úù"ñ 22:28
Subject: Cob: Insulation


>I have some ideas on insulation with cob which I would
>like to  begin testing next year (once we have some
>land).
>
>I had thought about straw bale cob hybrid with straw
>bale between cob walls but I do see some
>incompatablility here.  Straw needs to be very dry and
>with the moisture going through a breathing wall I am
>worried about moisture buldup in the straw thus
>rotting it.
>
>I would rather build a semi-double cob wall with air
>pockets through it.  These could be tubular running
>from top to bottom.  I would consider using a wicking
>material for the whole length of each tube to wick any
>moisture to evaporate in the attic.  I don't see this
>as a major source of moisture so a well ventilated
>attic should be able to dispell any moisture quite
>effectively.
>
>I would also like to fill each tube with ground up
>styrofoam waste -- coffee cups, meat trays, industrial
>leftovers etc.  This is a good insulator and is
>readily available with a bit of scrounging.  It is
>also not water retentive.  It settles minimally.
>
>Another avenue we are considering is a stack wall cob
>hybrid.  The more insulative stack wall would be the
>outside with a cob thermal mass interior.  Both walls
>breathe so they should be compatable.
>
>We would like to use cob for a few of reasons:
>
>*its flowing and sculpturable attributes
>*fireproof -- love to have candles all over in nooks
>and crannies
>*we can itegrate cob with the windows to create very
>interesting design
>*Cob is fun
>
>RC
>
>=====
>MistyMorning Designs
>www.localnet2000.net
>
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