Cob: New to this list and the idea of cob

[dtebb]

I live in Vancouver, British Columbia. The climate here may be considered
moderate, not as cold as Minnesota. I have been talking with an energy
engineer here who has "significant concerns" about cob as an insulator.
This engineer was unwilling to endorse cob unless it was an un-heated
building or used for interior walls. The r-values are just way too low and
he is not convinced that in as cold a climate as we have here, that the
thermal mass would work so well. We hardly get sun here in the winter, so
forget solar gain. He talked at length about technical issues that i barely
understood. He is also very intrigued by cob as low in embodied energy in
terms of no manufacturing of the material, the abundance of the material,
low cost and ability of almost anyone to learn this method. He did suggest
that a type of foam insulating layer would be something worth researching
or doing as they do with ramed earth.He would even support from a technical
side the research. How this may affect breathability and thermal mass is
not known but perhaps worth trying.

Now, there are a number of cob structures here in B.C. now and those living
in them report that they are comfortable. It would be very valuable
information to know how much energy they are using per sq. ft. to heat. It
is still possible that with good double or triple glazed windows, a well
insulated ceiling and other energy design features together with a good
thermal mass design, that minimizes loss in r-value. I came across some
data in a building book I have that states that infiltration (flow of air
in and out of the home through cracks) acounts for 55% of the heating load.
Whether accurate or not, it is something very important to consider.

So the question I have is how can we determine when and how the thermal
mass cancels out the loss in r-value? Where is the balance between the two?
How cold is too cold? How can we design for maximum thermal mass capability?

Ian

>Sharon,
>I think this is a very intereting idea. If you had a
>styrofoam wall, you could apply cob to both sides
>giving you an insulated mass inside with finished
>exterior. It may not be "green" and would probably
>need some engineering, but the concept is great. Lets
>do it. Know any engineers ?