Cob inside

[Shannon Dealy]

On Mon, 2 Sep 1996, Eric D. Hart wrote:

[SNIP]
>         Can cob posts be constructed?  I could see making a series of
> massive posts which were part of a strawbale infill system and which also
> provided thermal mass to the interior of the building.  When I am thinking
> about these ideas, I'm assuming that they would be tried in a place with no
> building codes.  I've got enough problems just trying to get strawbale in
> fill designs approved, let alone trying to add cob to the equation.  A cob
> column would work good in a greenhouse where you need thermal mass and some
> sort of material that will resist moisture damage.  One could start really
> early in the spring (after the ground thawed out) building your cob columns
> and then once they were ready,  put the roof trusses on them and then do the
> strawbale infill.  I can't see doing a whole wall that has such a poor
> R-value but using it sparingly for load bearing posts would be a good use of
> the material.  
> 

I would worry about constructing free standing cob posts, unless you give 
them a very broad base (perhaps tapering to the top) or an exceptionally 
strong tie at the top, since cob generally does not have any attachment 
to the ground other than gravity.  One earthquake and it's pancake city.


[SNIP]
>        One problem with masonry houses is that once they heat up, they stay
> that way for a while.  I went through an 1830's stone house on the
> Mississippi River here and they said that the house became unbearable in the
> summer, even in the relatively cool Minnesota summers.  The same goes for
> when the houses cool down, they get cool and stay that way.  Ever gone by a
> parking garage (all concrete) in the spring and early summer and felt how
> cold it is in there?  The inside of parking garages during the winter is
> colder than the outside air and stays that way longer (due to the poor
> insulation and the conductivity of the concrete).  I just envision living in
> a refrigerator during the winter and an oven during the summer, so am going
> to progress cautiously when it comes to using mass in buildings.  

I have seen a number of houses with this problem, it was usually due to 
having to much glass in the building.  During the summer, to much solar
radiation gets in and overheats the house and charges up the thermal mass,
then at night the thermal mass keeps it to hot.  During the winter, the
glass lets out more heat then can be collected, and you freeze.


>         Last question, have cob structures been built in places other than
> Oregon and Great Britian?  It may be that cob works well for places that
> have relatively mild climates and small temperature variations from season
> to season.  That's the climate in the Pacific Northwest and Great Britian
> but not the Midwest.  
> 
I am aware of cob structures having been constructed in Oregon, Washington,
California, New Mexico, Colorado, Mexico, British Columbia, Great Britain, 
and New Zealand.  Cob should be considered appropriate in most any 
climate, adobe is widely used in hot climates (cob is a form of adobe), 
and cob has historically been used in cool and wet climates.  It probably 
is not the best material for a really cold climate, but it is appropriate
for thermal mass, and is therefore a reasonable choice for south facing
walls in a really cold climate.  Ultimately, the real problem is to make 
sure that the building design takes into account the climate and the nature
of the building materials being used.  I have seen over the years numerous
structures that were designed to be impressive, and I'm sure I would have 
been really impressed by the enormous size of their heating bills.  The 
problem is not the materials that were used, but the way in which they 
were used.


Shannon Dealy
dealy at deatech.com