No, I don't generally sleep on the floor, but it does happen from time to time. I have a normal, western style bed (though twin beds tend to be slightly wider, so western sheets don't quite fit right). When I get really cold, though, I sometimes decide to sleep on the floor. Why on the floor? Isn't the floor cold and drafty? No, quite the opposite. The other night I was so cold I slept on the floor, which is what inspired me to write this post.
Koreans, many, many generations ago, developed what is known as ondol heating. The heat comes from the floor. Traditionally, the heat was made by burning wood or biomass of some sort a few times a day to keep the floors warm, but today homes are built with water pipes that run under the floors to heat them.
Koreans are very proud of their heating system. I suppose in theory it does make more sense... with heat rising and all that physics. They haven't quite figured out why the rest of the world hasn't picked up on the wondrous invention. I can think of some good reasons. For monetary reasons, I can't see people refitting their entire house to run water pipes under every floor. It's just not practical. There was a similar idea that caught on for a while in the US called radiant heating, where the heat came from the floor, but was produced electrically instead of by hot water pipes (think of an electric blanket for your floor). This was a good idea in theory, but at one time my old apartment in Vermont had radiant heating, but it was removed because it was causing the tenants to receive exorbitant electric bills in the winter. My electric bill already seemed expensive to me since we had electric hot water heating, I can't imagine what it was like with radiant heating.
Another reason why I don't think ondol heating has caught on in western cultures is the fact that we (westerners) don't spend much time on the floor. In traditional Korean culture, it makes all the sense in the world to heat the floor. That's where they would spend the most time in the past. Beds were mats on the floor and tables were about a foot off the ground with cushions for chairs. I feel as though ondol heating is becoming a bit antiquated as Korean culture becomes increasingly westernized. It's hard to find someone that sleeps on the floor, though it's not entirely unheard of. Most homes have normal tables like we're used to at home, and only bring out the low tables for sitting on the floor for special occasions. Let me tell you... when sitting in a normal chair, the only part of you that's warm is your feet. OK, that's not entirely true, but ondol heating tends to take a long time to heat up (like a few days to a week) and almost as long to cool down if it's too hot, though you'll rarely find me complaining about that.
Another handy thing to know about ondol is renting hotels in Korea. Most places have western beds, but if you're traveling in large groups, or looking for cheap prices check out an "ondol" room. This is basically just one big room where everyone can just sleep on the floor.
I would say maybe 10-20% of restaurants still have floor seating. These restaurants usually, but not always, have ondol heating. Ondol heating in public places/ businesses is less common. These are usually heated either by space heaters or wall units (or some combination of the two).
Going to the jjimjilbang is another place to see people sleeping and just chilling out on the floor. At most jjimjilbangs there are sleeping rooms where you can just pay a little more than a regular visit to the baths part and get a blanket and sleep in a dark room (another cheap way to travel in Korea). Sometimes people don't even get the sleeping rooms though. It's not uncommon for me to see men and women passed out on the floor in any position imaginable in the common area. I guess all the relaxation from the saunas and baths just puts them to sleep. No one would kick you out of a jjimjilbang, so I suspect that you could even sleep out there for the night if you wanted. Besides, laying out on a warm floor probably makes you sleepy anyway.
So, moral of the story? I think if I were ever in the position of having to rent and furnish my own Korean apartment, I think I'd go as traditional Korean as I could to take advantage of the ondol heating. I sort of prefer sitting on the floor sometimes, and I really don't mind sleeping on the floor.... Wow, just thinking about that makes me wish I could get rid of my table and bed right now.... the floor would be soooo warm right now........