Cob: Cob insulation idea

[Darel Henman]

lightearth at onebox.com wrote:
> 
> Cob has been used as a building material mostly in warm/hot climates such as the Zone 8 warmth of the Pacific northwest or the desert and such.

This is only very partially correct.   Cob has been used for over
hundreds of years in the cold and wet areas of the United Kingdom, and a
form of wattle and daub was in use in Japan.  These are cold winter
regions.

>...we're doing a modified Cordwood structure using Cob instead of cement and insulating between the outter layer of cob/wood and the inner wall because we're in the Great Lakes area that gets very cold and stays there for months!

Insulation on the outer layers of the north, east and west side would
perform even better, but, wouldn't look as nice.


> No , Cob isn't a real great insulator but it makes good thermal mass which is good if the days warm up some (After a cooler night)but really SUCKS if they stay below freezing (and below zero for periods) for along time as they'll radiate your internal heat out through the walls and build up a cold so deep it'll take alot of energy to warm those walls up!

Not if you have store up enough thermal energy to carry you over the lag
time till it warms up again.  This is how earthships and annualar
thermal storage systems work.  Insulation on the north,west, and east
sides would increase performance.  Adding solar heaters would help as
well.   Basically you only need to store enough thermal energy to carry
you through cloudy spells which may last up to a week or two.  Depending
on your area. 

> 
> Also the thermal mass on the INSIDE of an insulated (or call it OUTSULATED) Cob wall helps to store the internal heat generated inside the building as it can't so easily escape out to the cold outside...

Yes, this is right, but you might want it to collect solar heat from the
sun on the south side, unless you can funnel in solar heat from some
other mechanism.

> This is another reason that people use Strawbale walls instead of Cob, for alot of insulation....we're trying to hybridize something that utilizes CITY waste streams with natural earth i.e. - 2x4's, clay, sand, waste paper+other non-toxic insulating ingredients!

Unfortunately cob would not carry you through cold spells like a good
charged thermal mass would.  
The hybrid idea you have is very good.  Strawbale might be considered
for the north wall on the outside and inside have a thick cob finish. 
This will help moderate humidity in the house as well.

Darel