Hopefully someone with more knowledge will jump in here, but one thing I can contribute is that AAC is not waterproof. I have no idea if it's strong enough for a retaining wall, but you can reinforce it by placing rebar down into holes into the AAC then grouting it solid.

I have built earthsheltered since the early 70's and I have extensive experience worldwide with aerated cellular concrete.  I am not saying all of that makes me an expert but I would caution you to study some more.
AAC is NOT waterproof and when you aerate concrete you weaken it significatly.  These things can be mitigated with proper engineering design but that is done by a qualified professional.  Even professionals make mistakes  (look up how Ken Kern died for instance)
AAC and aerated cellular both have their place but probably not as a below grade foundation/retaining wall--at least not without very qualified engineering oversight.

Thanks guys, I really appreciate the responses. I am researching as many materials as I can find and when I began reading about AAC I thought I may have stumbled upon a good idea, I guess not.


Thanks for sharing you knowledge.

Isn't this a great forum?!

Anyone use this product?

A waterproof concrete: http://www.hycrete.com/

After 19 years in an earth sheltered home I recomend you save the money on insulation.
Make that inside to outside: concrete, waterproofing, drainage to perimater drain (french drain), earth.  Your counting on thermal mass of concrete, why not include the earth around you! It won't remain 55°F but have a heat affected zone out to about 50" max.  Thermal mass is nice.  I had 8 days of snowed in, no power, no heat except passive solar and inside temp dropped 2°F to 70°F. If you have exposed walls insulate to below frost line. Also as part of your waterproofing slope dirt away from house, no standing water to challenge waterproofing!  Also get your retaining walls engineered!

Check out Preformance Building Systems of Durango colorado. After 19 years in mine I strongly recomende them.
                                               earthshelter.com

I don't speak from any experience, but I am attracted to the idea of using AAC blocks for the under ground portion of my future home mainly for its superb insulating properties, and its usefulness in aboveground construction. My research finds that AAC is in fact used for basements, and therefore should be practical for an earth sheltered wall.


7. Can this product be used for basement walls?
Yes. The walls must be designed correctly to account for axial loads when used as a basement retaining wall. Due to the extreme horizontal pressures exerted by backfilling, thicker walls with additional vertical conrete and rebar reinforcement should be used, as specified by a qualified structural engineer. All walls below grade should be waterproofed as discussed above.
http://www.safecrete.com/aac/faq.cfm#6

When AAC panels are used in contact with moist or saturated soil (for example, in basement walls), the surface in contact with the soil should be coated with a waterproof material or membrane. The interior surface should either remain uncoated, or be coated with a vapor-permeable interior finish.
http://www.masonrymagazine.com/6-08/autoclaved.html

Q: Would AAC be applicable for earth sheltered construction?

A: (Kelly) I see no reason why not to use AAC for earth-sheltered construction. They claim that it does not wick moisture, but as a precaution, I would suggest using an additional moisture barrier in any bermed locations. With its insulative qualities, I would think that AAC would indeed be a good choice.

http://www.greenhomebuilding.com/QandA/manufactured/aac.htm

AAC can be used as a retaining wall, when you add reinforcement. You also have to use a waterproofer

Guys - I have a new product that could be of interest to you and some of your questions. I'm not a builder but I do have some information which not only is new, unique, green but also has already gone thru many of the certified testing requirements. I'm on the sales side of things and have an opportunity to pick up this product as one of our lines. I hope this web-site is helpful and I'd appreciate your feedback since you're all the professionals and the best people qualified to tell me if this is a product worth attaining. www.apexconsys.com Hope to hear back from you all.

Why not forget the Berm and just insulate the outside of the thermal mass as in .....

http://www.tierraconcretehomes.com/constructionmethods.html

http://www.thenaturalhome.com/passivesolar.html

The apex block insulates the thermal mass away from the interior as do ICF's ... i feel that is counter productive