I am very interested in building an earth sheltered home.

From what I have read so far, you want the insulation, and waterproofing on the outside.  So it goes, from inside to outside: concrete, insulation, waterproofing, protection / drainage layer, gravel, earth.

This gives you a large dry interior thermal mass that is insulated from a constant exterior temperture of 55 degrees.

 

I have started to read about aerated concrete and am trying to figure out if it would be a good option for the wall. 

It is waterproof.

 

It has a higher r-value than concrete. 

Reduces thermal bridging.

 

It is vapor permeable, so it breathes.

I think that these are good qualities, from what I understand, you want your wall to dry from the inside and I think the AAC might be less damp than regular concrete in this situation.

 

I may be completely off base and it may be a stupid idea.  It may not be strong enough for a retaining wall.  

Thoughts?