In cold winter, people in Northeast China have a habit of sleeping on heated brick beds, which are usually made of sun-dried mud bricks or house bricks with kraft paper spread on top. After being painted, they are clean, simple and nice to use.
Actually, it is scientifically proven to be good to sleep on heated brick beds. Usually, these beds are built in the inner rooms while cooking ranges are on the outside of the houses. When cooking, the heat exhausts given out by the fire go through the flues under the bed and then come out through chimneys. Cooking thrice a day heats the beds three times and the heat from cooking is, therefore, enough to keep the beds warm and comfortable for a whole day.