[Cob] insulation

[Rodger Chenoweth]

Hi Roselle,
I just helped build a cob house that had it's north wall a double cob  
wall cordwood hybrid.  18 inches thick, with 6 inches cob, 6 inches  
sawdust/lime insulation, 6 inches cob... with the cob walls bound  
together by cordwood (about 20 inches long each) that bridges the  
three layers.  Personally, I think  strawbale is wonderful for cold  
climates, but if it's a WET cold climate, then I think cob cordwood  
is the way to go.

WAY less cob to mix, doesn't shrink like mortar would, and if it does  
who cares, just patch it up with an earthen plaster.  The R value for  
a 24 inch thick cordwood wall is in the region of 25-30, which is  
about what code specifies.

The final look is gorgeous too, and the wood ends keep people/ 
furniture/dogs etc.. from hitting the cob so it's nicely protected.

AND IT BREATHES.

Cheers
Rodger

On 17-Jan-06, at 9:32 AM, Roselle Milvich wrote:

> Hi,
>
> I am very interested in cob, and one hurdle I'm trying
> to overcome is the issue of insulation in cold
> climates.  I just heard of someone locally who just
> tore down a cob building because it was a major cold
> sink.  I'm in the san juan mountains of colorado.
>
> I've read ideas of outsulating on this list.  It
> sounds like it has too many problems. Has anyone tried
> insulating from the inside?  I'm seeing the benefits
> of:
>
> 	The insulation/inside walls could be built in the
> fall or winter allowing more summer time for the
> construction of the basic structure.
> 	The insulation would be more protected, allowing more
> options for materials.   So far I think I've just
> heard of strawbale for outsulating which would add
> dramatically to the width of the walls and would have
> to be protected well from the weather.  I've heard of
> a double wall system that uses other materials, but
> that sounds like it would compromise the strength of
> the wall and would require more of a foundation.  I'm
> thinking I could use a smaller foundation for the
> inner wall.
> 	Too much thermal mass may be a bad thing in cold
> climates.  It would be heating unlivable space.  I
> don't think I'd want much more thermal mass than the
> what the sun could heat-up.   Most of the solar gain
> would be from direct sunlight coming through the
> windows.  It would be good to have some additional
> thermal mass for evening out the temperatures, but I
> think an inner wall, some built in furniture, and an
> adobe floor would be plenty.
>
> I'm still not sure about the north wall.  Without the
> sun, I think its temperature may be close to the
> night-time temperatures during the day.  Or is it that
> way with all building types?  I think the other walls
> would gain enough sunshine to help balance out the
> temperature slightly at night.  I don't know how much
> the north wall could hurt.  Maybe a hybrid with
> strawbale would be better.  I prefer the simplicity of
> just using the cob, but maybe its not worth it.  Or is
> strawbale a better option for me?  It isn't nearly as
> appealing.  I like the sculptural qualities and
> simplicity of cob.  And I just like dirt.
>
> I'm making a lot of guesses here.  Has anyone
> experimented with insulation?  How did those double
> walls perform?
>
> Thanks,
> Roselle
>
> __________________________________________________
> Do You Yahoo!?
> Tired of spam?  Yahoo! Mail has the best spam protection around
> http://mail.yahoo.com
>
> _______________________________________________
> Coblist mailing list
> Coblist at deatech.com
> http://www.deatech.com/mailman/listinfo/coblist