RJT> I know of at least one house around here that's built exactly as
  > described, in that it's significantly under the ground, with only
  > a south-facing full face exposed.
RJT> I don't know the details of the construction, or how their
  > heating bills compare with more typical construction, but I'm
  > sure that the place *had* to pass an inspection before they
  > issued a certificate of occupancy.
 TH> Building codes vary widely from county to county. Some counties 
 TH> do very little inspection. They figure that you better know 
 TH> what you are doing, or no one's going to buy your house. 
Actually,  around here they vary from one township to the next.  But I think 
that you still need that CO before you're legally allowed to move in and 
occupy the place.  I'm not sure how consistent that requirement is.
Other inspection requirements (plumbing,  electrical) are definitely going to 
vary from one place to another.  I know that Harrisburg,  for example,  
requires electricians to be licensed (which I was used to from the NYC area). 
On the other hand,  lots of places have no such requirements.  There was one 
place where I lived where my workbench was right directly above the breaker 
box in the cellar,  and when I called the township to find out if they had 
any particular requirements,  they told me there were none.
 TH> As for as energy savings, I think most places insulate the 
 TH> perimeter walls, floor and ceiling. I think that's a shame, 
 TH> since so much mass could be used to maintain a constant 
 TH> tempreture.
I imagine that a place like the one I was referring to up there would have 
some pretty specific requirements for the walls,  both to support the weight 
of the dirt piled up against them and to keep moisture seepage from rotting 
things out.
Seems do-able,  though!
I wonder what it cost them,  comparatively?  I'll bet that it cost them more 
than a typical house would have,  but then you've got lower energy costs for 
the life of the place,  I wonder what the payback period is?
Hmm...
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