They are very good insulators, making this a wonderful building material for the desert.

As I recall, they are even better than that: they are a heat sink, that will will warm with and thus "store up" the heat of the day. Thus a good portion of the heat of the desert will go into heating the bricks -- rather than heating the interior of the home -- and a part of stored heat, the warmth of the adobe brick, will then go to radiating and warming the home during the cool desert night.

Much the same effect is felt in a well-built fireplace in an older home. Even after the fire is out, the heat of the brick or stone lining the firebed will radiate out and greatly warm the room for over an hour.

I wonder if the typical thickness of an adobe brick is not random, but rather is the thickness such that it takes 12 hours for heat, at the exterior side, to pass through and warm the interior side.

Perhaps stales, or jazzo, might have some information on this?