Cob: Re: Thermal Mass and R-values

[Tony Glaser]

I want to build a cob home in Canada where it sometimes gets as cold as
-35 degrees Celcius, so I want to be clear on this issue which you cobbers
have been discussing for some time (as I see in the archives).

As I understand it, thermal mass is how much heat your walls can store,
and insulation is how slowly heat is put in or taken out.

If Cob has a high thermal mass and a low insulation, that must mean that
you can store a lot of heat in it, but the heat also enters and leaves
quickly.

So in the winter I want the outside of my wall which faces away form the
sun (north) to be as insulated as much as possible, all of the time.  The
side which faces the sun should be insulated as much as possible at night,
but in the day insulated _just_enough_ so that the sun can transfer it's
energy into the wall at the rate it wants to.

In the summer, I wan't shade and no insulation, but lots of thermal mass.
(Which is why cob is so great for warm climates.)

So as far as I can tel, the easiest thing to do is stack straw bales
around the shaded parts of your house in the winter (adding some to the
front at night if its cold enough to freeze the balls off a brass monkey),
and move the bales away in the summer.

I guess an advantage to this is that the bales will collect snow, which is
itself a great insulator, and looks pretty.

This is what I'll do unless someone has some better advice.

Thanks,

Tony

--------------------------------------------
Anthony Glaser
aglaser at engsoc.carleton.ca
http://www.engsoc.carleton.ca/~aglaser
Year 2 Electrical
Faculty of Engineering, Carleton University