The early medieval farmhouses and city dwellings were heated with an open hearth surrounded by stones. This was also used for cooking. The smoke simply evaporated through gaps or open patches in the ceiling. Later on funnel-shaped flues over the fireplace directed the smoke outside through a hole in the roof.
Heating by open fire posed a huge fire hazard for the houses built out of straw and wood. With the increase in housing density Braunschweig repeatedly suffered large city fires.
From about the 13th century onwards the stone bowers were heated with open fireplaces. These were mainly situated in a corner on the upper floor and connected to flues throughout all storeys. That system also heated the other rooms in the house and the smoke was guided directly to the outside.
Some old bowers even had floor insulation. A row of clay pots standing upside down underneath the floor collected moisture and hence insulated against the cold.
Tiled stoves were invented during the Middle Ages. They had the advantage of being able to heat the house smoke-free. The oven stood along a wall and was fuelled from an opening into the adjacent room which was mostly the kitchen. The bricks and tiles that were used stored the heat and then gave off that heat. As there were no more open fires the fire risk dropped considerably. This solution also had another advantage: you could bake with this. Such rooms heated by tiled stoves were to be found in all well-equipped middle-class houses. They were called ‘Stube’ (after extufa-oven) or ‘Dornse’ (after domica-heated room).