Cob: Thermal mass and climate

[Darel Henman]

Kerry,
  see my comments below:

Kerry S Tebbetts wrote:
> 
> However, as I pointed
> out, there's that thermal flywheel effect doing a nasty number on us in the summer.

Kerry have you ever made any temperature and humidity measurements for
both inside and outside for comparison.  A previous e-mail to the group
menetioned this.

> So, what's the solution for staying cool in the summer?
Shade.  Time to bring out the:
  a.) canvas tarp to spread across a frame to shade the house, or
  b.) mats of reeds, etc, woven together to let the wind through, but
not the direct sunlight.
  c.) the grape vines you planted should be creating nice shade for the
house. 
  d.) the bamboo you cut down in the winter has now grown up so tall it
shades the vertical (walls of the) sides of the house most of the day?
 
Plants will evapotransire(?) and cool the area around the structure.  If
your cob walls absorbed some moisture from humid weather it also will
evaporate and cool the inside.

> Is the answer to
> block solar gain by using exterior insulation?
Certainly not on the south side, unless you have some othere mechanism
to get the solar heat inside.
Insulation could be done on the north, east, and west sides.

Tell us about your attic?   Have you put any thought to its contribution
to the heat in the house, during the summer?  

> but has anyone thought of a way
> of using it (water) for cooling - even in humid climates where the roof pool and
> earth tubes aren't advisable?

Earth tubes should be fine anywhere.  Why do you feel its inadvisable?

> Could you not strategically place
> containers of water around and/or in your house, allow them to heat up
> all day, and them empty them before their thermal load is reached at
> which point they'll start to radiate heat in your house? 

Yes and then pump it out to cool at night then bring it back in at 7:00
A.M. or so when its temperature is as low as it'll get.   But not to a
roof pool.   Use as shallow and large an area as possible, so that it
would cool of faster.  But since it has all night, you have to think
about the suitable surface area to let the heat come out.  It would
radiate heat to the great heat sink, space.   Radiation flies in direct
lines.  That's why frost on car's usually happens on the tops first. 
The heat is leaving it faster.

Use P.V. panels for charging the batteries for the pumps, or to a P.V.
direct and only pump when the sun is up, but this would limit operating
times to morning and evening and the collector's angle would have to be
adjusted twice daily.

> I don't know if this water would be kept separate from
> the wall in plastic or metal containers or if it would be incorporated
> into the cob wall.
You could do either.  Some have considered putting through the floor
and/or up into the northern wall so that solar collector heat could be
used to heat it up in the winter. 


>  The thing I don't exactly understand is how condensation might pose a problem?
For walls, it shouldn't be a problem if you used natural breathable
finishes or beautiful mud plasters.

> If the containers were embedded in the wall, would condensation occur inside the cob?
I'd have to guess on this and say no.  I recall reading something about
this and it said it wouldn't be a problem.  There may not be that much
of a temperature difference to cause condensation.  All moisture would
have to come from the cob itself, unless you don't have the pipes sealed
off.

> How would heat travel
> through a "cob water wall"?
This is a cob wall with water tubes in it?


> Would it travel through the cob and then get stored in the water more so than the cob?
> Or would it be stored in the exterior and interior cob more so than the water?
It would store the same amount of energy, if you think of it as a static
system.
Having water in the wall would slow down temperature changes, but the
amount of thermal energy stored or sank in the wall would be the same.  
Energy out = Energy in - (Energy stored temporarily)

> Shae

You have some great ideas.  Keep it up.   I don't know to call you Shae
or Kerry, but whatever.  Keep up the flow of ideas.

Darel