The Rare Norm a few months ago Share Tweet Pin Share This thing is beautiful, but the 2+ hour preheat and the straight chimney and open door tells me this thing is wasting 90%-95%, or more of the heat energy up the chimney. An interior fireplace is only around 15% efficient, so an exterior fireplace with a short chimney must be only a fraction as good as that. For comparison, a wood stove can approach 80% efficient under ideal conditions, but is typically around 70%. It probably isn’t going to be used all the time so that may not be a big deal to anyone but as an engineer and as someone always scrounging for firewood my eye twitched a little. EDIT: I seem to have confused people. I was not suggesting you could somehow heat a brick oven in minutes, nor was I claiming that since this one takes 2 hours it’s “inefficient.” Even if that were possible the bricks would probably shatter or explode. My issue is that some 95% of the heat is still going up the chimney, so you are burning 20X the wood you need to, and releasing 20X the pollution you need to.