Jeremy Bunag wrote:But I'm imagining something like sandbags (or dirtbags) stacked up, with little fissures for air to infiltrate.
Seems to me that that is the last thing to worry about with this kind of construction. Earth bags are the exact same thing as sand bags used to hold back flood waters. Indeed most 'sand bagging' uses local soil rather than sand. Those hand stacked bags lock into each other so tightly that water can't get through even though the bag is made of open weave plastic and filled with permeable soil.
Thermal mass structures, especially in 4 season zones, are improved with insulation on the outside. I read of using vermiculite or expanded perlite render to plaster the exterior walls. But the discussion of rice hulls got me thinking - what about an outer row of rice hull bags next to the soil bags? Would they be stable enough to apply an external cob render over them?
There are immense quantities of shredded wood chips/mulch (not talking about leaf mulch) in many areas. A lot is used in gardening as ground cover. But the supply is nearly free if you have a chipper and brush to clear, or are willing to haul it away for others. Would this be useful in bags? It would be a lot better insulator than as thermal mass, and you'd need to be extra careful in providing a vapor barrier. Seems like it could compliment cordwood construction using on site dead trees and underbrush as building material. Most trees aren't suitable for lumber, but they could still provide useful building material.