Cob: RE: Re: INSULATION FACTS

[John Schinnerer]

Aloha,

-----Original Message-----
From: DoNegard at aol.com [mailto:DoNegard at aol.com]
> 3. Does R-value as standardly tested, really the same as comfort level.  I

>have heard the numbers for earth for a while, and I am not yet convinced
that 
>all materials that give the same R-value, will also give the same comfort.
 
Definitely not.  Your comment...

>One thing I know for sure about interior house walls: if they are very cold

>to touch in the winter, the room is going to feel "too cool". 

...is right on.  Humans sense heat and "coolth" in several ways -
conduction, convection and radiance.  

Conduction is feeling warmer or cooler due to direct contact with warmer or
cooler surfaces.  

Radiance is feeling warmer or cooler because the surrounding surfaces are
warmer or cooler 

Convection has to do with air flow moving heat/"coolth" around, making us
feel warmer or cooler.  This one is a bit more complex, because it combines
air temperature with volume of air moving over our bodies (for example, all
else being equal, 65 degrees and calm may be perfect for me, but 65 degrees
and 10 mph wind may be too chilly after a while...70 degrees may be fine at
10 mph but at 15 mph it may get chilly after a while...).  In short, all
else being equal a drafty house will feel colder than a snug one on a cold
day because of more air movement carrying heat away from my body.

R-value of walls and/or roof is a *very* limited indicator of overall
interior comfort, and as someone pointed out has been inflated to the status
of "all there is" by the industrial housing/insulation industry.  

Focusing on the R-value of cob is to me silly, because cob is not primarily
an insulative material, it is primarily a thermal mass material.  In
locations where thermal mass alone will not "work" for whatever reasons
(lack of sun for passive solar, not wanting to run a woodstove all winter,
etc. etc.) cob alone will not work - and it may or may not be useful as part
of a structure, depending on how and where it is used.

John Schinnerer