TH> And it only works if the average temperature is within the
  > confort zone. Yuma, Arizona might work, but Fairbanks, Alaska
  > would not.
 
TH> Still, in principle I'm with you.  I don't know about that. If you insulated around the outside of
  > the thermal mass as well, it'd be possible. Whether or not it'd
  > be economicly feasible, is another story.
Yes, it's the *other* story that ones pocketbook *has* to read. 
 
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