One of the great things about Korea is its floor heating system, call the ondol. Although it's not always standard to have a heater, every apartment will have an ondol. They are also common at restaurants where you sit on the floor. Our apartment has two, for half sections of our floor. Each section has it's own control panel on the wall by our front door. I suppose this would be handy if we slept on the floor, cutting the heating cost so that only the sleeping area would be hot at night.
Ours actually doesn't get that hot, because our building was set up to be energy efficient and environmentally friendly, so it starts storing energy during the day and only gets warm at night. With the windows close, it does help to warm the apartment gradually. As we have a western style bed, we don't have much use for it when we sleep. However, there are other ways to benefit from this system. I've found that laying my clothes for work in the morning out on the floor results in the same joy as wrapping up in a blanket fresh out of the dryer. Also, the space and concrete support needed for the ondol keeps apartments from having those paper-thin barriers between the floors; something I would have loved in college.