Cob: strawbale/cob on the inside

[Paul]

	True, no uninsulated walls can collect and hold enough heat for those
temperatures. But no INsulated walls can either. To fight that long term
ambient cold you need long term ambient heat from the earth beneath. The
simple way to get it is perimeter insulation. 3-inch or more foam board 3-6
feet into the ground around the outside of the foundation, with moisture
barrier to keep the earth under the subfloor or slab dry and warm. And you
don't have to rely on walls to hold the heat. You can put a thermal mass
gravel bed under a subfloor for direct gain from south glass, and cover the
glass with insulated shutters during non-solar gain hours or days. You can
bury the house four feet deep or berm it four feet too, but always using
perimeter insulation and moisture barrier for the foundation and walls. In
my state, perimeter insulation is actually code.

--paul, webmaster http://globalcircle.net
peace and liberty, sustainability and justice
*********** REPLY SEPARATOR  ***********

On 2/13/02 at 9:26 AM Tom Fetter wrote:

>As another Albertan interested in cob buildings, I've been a bit
>surprised 
>that some folks haven't realized the necessity of insulation when building

>in as extreme a climate as this one.  There's simply no way that an 
>uninsulated wall of any material can collect and hold enough solar gain to

>counter weeks on end of daytime temperatures averaging -20 degrees, with 
>night temperatures another 10-15 degrees colder.  Even the most efficient 
>thermal flywheel has to deal with long-term ambient temperature as well as

>solar gain.  I have also wondered about a hybrid, using strawbales on the 
>outside, cob on the inside ... or maybe a 4-6 inch thick layer of 
>cob/earthen plaster on the inside of strawbales to get the thermal mass 
>benefits.
>
>The stumbling block in my mind has always been how to adequately protect
>an 
>external earthen plaster from cracking/spalling in the repeated
>freeze/thaw 
>cycles we regularly have at either end of the winter.  Through November,
>and 
>then again for about 7 weeks in early Spring, we often have humid days (as

>snow/ice melts) and freezing nights. This regularly cracks commercial
>bricks 
>that haven't been fired at high enough temperatures to resist taking up 
>moisture.  Given that, it makes me feel doubtful that a wide roof overhang

>and a high foundation would be adequate to protect unfired earth.  I'd 
>appreciate any ideas ....
>
>Tom Fetter.
>
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