Bohlenstube

Machine-translated from the German article

In the Middle Ages, the Bohlenstube was often the only heated room in a house in Central Europe. To improve thermal insulation, existing rooms were lined on the floor, ceiling and all sides with tongue-and-groove wooden planks; that is, a further room was built of wood inside an existing room, structurally separated from the outer one. To avoid having to heat too large a volume of space, the ceilings were sometimes lowered.