Factors that must work are: the draft of the chimney and the heating curve and retention of the oven mass. Without these two factors performing well, if not perfectly, the fun and beauty of the experience will be lost. Adequate mass combined with sufficient insulation makes the brick oven an efficient device.
|Cob oven w/o chimney vented with massive hood|
#3 Convenient use decreases apparent cost. A snowmobile in Alaska is a constant tool. Brick ovens should be sited so that they get used, if not daily, weekly. If the oven is associated with a space that is a major living space (outdoors, adjacent to the kitchen, or in the the kitchen) it will be used frequently.
Thinking out of the box about community brick ovens would include a traveling oven that could serve multiple communities by relocating on a rotating schedule.