How does the Korean floor heating system (ondol) work, and how do I operate the boiler in my apartment?

Ondol is Korea's underfloor heating, and once you get used to warm floors you will not want radiators again. Modern apartments heat water in a boiler and circulate it through pipes under the floor, so the heat rises evenly and the floor itself is cozy to sit and sleep on. The control panel on your wall usually has two main modes: 실내 (room), which heats based on the air temperature in the room, and 온돌 (ondol), which heats based on the floor and water temperature directly. For everyday use, 실내 mode set around 22 to 24 degrees works well and is more economical, because it stops once the room hits your target.

There is also an 외출 (away) button for when you go out, which keeps the place from getting too cold without fully heating, and a 예약 (timer) function. The same boiler controls your hot water, and the 온수 setting adjusts shower temperature. A big tip for saving on gas bills is to keep a steady moderate temperature rather than blasting it then shutting it off, since reheating a cold concrete floor uses more energy. If your panel only shows Korean, the common labels are 운전 (power), 온도 (temperature), 온수 (hot water), 외출 (out), and 예약 (timer). Boilers are usually Kyungdong, Rinnai, or Navien, and most have nearly identical layouts.