From Low-Tech Magazine, a lengthy article on "oven-stoves"--ceramic or stone stoves--designed to provide heat throughout the day (or night) on less fuel than a conventional wood stove or fireplace. The article also has numerous photographs of different designs and styles.
The most essential feature of an oven stove is that it is made out of some kind of stone or brick, while all our modern heating appliances are made of steel. Metal heats up fast, but it also cools down just as quickly. Therefore, a metal heating appliance has to be fuelled almost continuously.Read the whole thing.
Stone requires more time to heat up, but once it has, it holds the heat much longer. An oven stove is only fired for a short time, from a quarter of an hour to one or two hours and only once or twice per day. An average oven stove then radiates heat for at least 12 hours.
The main part of the heating appliance consists of a labyrinth of smoke channels and smoke rooms. Their aim is to hold the warm gasses inside the oven as long as possible, so that the stone can absorb the heat before it leaves the chimney.
The energetic output of an oven stove is 80 to 90 percent, compared to 40 to 50 percent for metal stoves or central heating appliances, and only 10 to 15 percent for a fireplace – where most heat escapes via the chimney. One of the most striking features of a (wood fuelled) oven stove is the stokehold, which looks ridiculously small compared to the stove itself.
Thanks to the high output, a modest masonry heater or tile stove (heating a room of 60 square meters) only needs 6 cubic meters of wood per year: one tree. If you have even a small garden, you can easily fuel your oven stove by means of your own cuttings – thin wood is very well suited for tile stoves, although it needs to be dry enough.
All our contemporary heating appliances warm a house or a room mainly by means of convection: they heat up the air. An oven stove does it by means of radiant heat: infrared radiation, comparable to the heat of the sun. In a room that is heated by an oven stove, a thermometer can hardly measure anything.
The effect is comparable to that of a skier who enjoys a schnapps while sunbathing, in spite of the freezing temperatures. Radiant heat does not (only) warm up the air, but particularly also the body of the skier directly.
An oven stove acts in the same way as the sun: it does not so much heat the air, but the floor, the walls, the furniture and the people in the room. These objects in their turn radiate that absorbed heat to their environment – similar to a city radiating heat after a long hot summer day, when the walls and the pavement slowly release back the heat from the sun.