Stay toasty warm the Korean way
Ondol transmits the smoke generated by a furnace through an underfloor system placed throughout the house.
Unlike radiators, which heat only the immediate vicinity, and heaters, which decrease the humidity in the air, making skin dry, ondol functions as a humidity control system. When building homes, ancient Koreans first laid down a foundation of thick stones with a passageway for the smoke and then covered the stones with oiled paper. To keep the smoke from coming out of the stone foundation when the stones were heated, it was common to place a layer of clay over the stones. The clay also helped control humidity in the room.
Ondol is energy efficient because only one fire was needed to heat an entire house, unlike old European houses where each room had a fireplace. In this way, ondol has a dual function. The fire that is made for cooking in the kitchen also heats the rooms in the rest of the house.
To transmit heat quickly to the other rooms in the house, the stones in the room that’s adjacent to the kitchen are thinner than the stones on the other side. This arrangement also helped slow down the transmission of heat to prevent overheating in individual rooms.
The area with the thinner stones in each room is called the araetmok. The side of the room with the thicker stones is called the witmok.
Because the witmok is colder than the araetmok, the oldest members of a household or important guests were seated over the araetmok.
Though the underfloor heating system kept houses warm in winter, it also had some shortcomings. To maintain the temperature of a room, doors and windows had to be kept closed. This could eventually lead to dryness and a lack of ventilation. It was also difficult to estimate how much time was needed to heat the stones, and the room temperature could be difficult to control.
By Lee Sun-min