I agree with tim on one thing there, a vapor barrier when dealing with a clay wall is not a good idea. The reason is that clay needs to be able to breathe and move moisture throughout itself to function properly, and I suspect with clay straw, a vapor barrier would hasten the deterioration of the wall materials.

An air barrier, however, is a must for a modern American house. Especially so if we are building for profit.

You should read up on straw clay walls in Germany, where they are typically at least 12" thick, and are both an infill and an envelope. 'Wrap and Fill' you might call it.

Another technique, which I learned from the Swiss, but the Germans use too at times, is to have a layer of tongue and grooved planking set into the timbers and plastered on both sides. Many Swiss half timbered homes actually have this in the cavities instead of masonry. This creates an effective draft barrier.

Japanese TV is so weird... I like the fiddle tune goin on in the background to let the Japanese know these folks are Americans! Think I'll go play my fiddle now...

DLB