Cob: to insulate or not

[Drew Neve]

I'm going to disagree with most of the comments questioning what I said,
based on the source I quoted in the original message and my own
experiences.  If I go into my 40 degree uninsulated basement and put on a
space heater while I'm working on something, the temperature warms up right
nearby the heater only.  If I take that same heater to the same sized
insulated room immediately above, even at night, the heat warms the entire
room, even when it is below zero outside.  As soon as I set the heater down
and walk back downstairs, the temperature still says 40 degrees.
Apparently that heat is being absorbed by the earth outside my basement
walls.  A thermal mass will hold heat, but the earth is more of a thermal
mass than I am interested in heating.  I also don't want to live in a 40
degree house, so I'm going to insulate against the earth.
Also, looking at the figure in "The Hand-Scupted House" that compares cob
to straw bales, they point out that cob (earth) is not a good insulator.
I don't know Darel, and I don't want to be confrontational, but I find his
points puzzling, perhaps there is a misunderstanding as to the context.
All of this really is not peculiar to cob.  As an aside I would not
recommend using cob below grade, pour concrete or use stone or earth-filled
tires against the hill and use cob above grade.

Drew Neve


Darel Henman wrote:

> Drew Neve wrote:
> >
> > The earth is a terrible insulator so you do
> > want to insulate that rear wall.
>
> This statement is not accurate, except in one dimension.
> Earth itself, when considering its thermal characterics together show
> that it has very good temperature control ability in its thermal mass.
> It will not loose heat quickly and will not absorb quickly.  It will
> once heated up to a comfortable level, maintain that level and prevent
> quick chilling or over heating in a house.
>
> > Using the rear rooms for storage does
> > provide further insulation for the living areas and keep them more
> > comfortable.
> This is good common sense, for the north side of a house in the northern
> hemisphere.
>
> > The advantage to being against the earth is that you are
> > insulating against 40 degrees instead of -20 degrees (around here),
>
> Not if the earth pocket is charged up to 80 degrees in the summer.  It
> would stay the temperature or down to about 65 during the end of
> winter.
>
> >.....but the earth will absorb the heat if you don't insulate.
>
> Not if it was charged up to the 80 degree level.  In this case it would
> provide heat for the house.
>
> Some clever people put an insulative umbrella from the outside of the
> foundation and down and out away from the house for about 10 to 20 feet
> to use the earth below it as a thermal storage area to float the house
> at a comfortable temperature throughout winter.
>
> This is just another way that it can be done.
>
> Darel