Insulation is key we use a thermic insulation blanket to retain the heat by helping the oven to heat up fast and stop heat escaping through the outer wall. Keeping the heat in means the oven is very low on wood consumption. Also as a safety feature it keeps the outer dome from getting to hot.  The insulation blanket has a waterproof layer to stop moisture entering the cooking chamber which makes the chamber quicker to heat to the desired cooking temperature .  

 The brick chamber absorbers  and retains the heat from the fire the result being good heat consistency over a long period of time.