There are various types of housing in Korea that include apartments, studios, jutaek, sataek, hanok, villas (pronounced as billa in Korea), goshiwons and key-suksa (dorms) to name a few. We lived in a jutaek and a billa in Seoul, both were huge.
Jutaek or Tha Khagu Jib (다가구집): houses in this genre were built some 30 years ago. If you have been to Itaewon, Noksapyeong, Hannamdong, Bokwang-dong in Yonsan district the majority of the houses are still villa (billa) or Tha-Kha-gu-jib.
All of these houses have an old style floor heating system "ONDOL" or (온돌).
Ondol is Korea's oldest and most loved inventions. Different people have different opinions about ondol. I remember that my German friend used to say that heated floors gave her feet burns. Some others said that, since windows are not properly sealed ondol doesn't warm up the rooms properly and one feels cold. Another friend, whose mom was quite old, always said that they needed ondol plus a heater to keep her warm and comfortable.
Either you love it or hate it , this is what we have in Korea to heat up the icy rooms and hence, you will NOT see heaters in building old or new. However, that doesn't mean that there are no heaters. There is an option of a gas heater as well as an electric heater. If you use only electric heater your bill is going to be 50% less approximately than what it usually costs using ondol only. Personally, I've experienced ondol by gas, oil and also wood for really long or short durations in different cities in Korea. It is an interesting experience indeed BUT it is very expensive.
I still remember that we paid 450 to 500 dollars for our heating bill during one winter - for heating four rooms including a kitchen. Our minimum ondol bill was 350USD or 350,000 won.
Nobody told me what could be the alternative of ondol? If you will ask me then I will highly recommend you to buy an electric heater (portable or space heater) and even if you will NOT turn it off the entire month, the bill will be about 30USD-40USD ( depending on the size of the heater, though). I discovered it after paying huge ondol bills for 7 damn years. So now, that the winters are just around the corner, try to get yourself an electric heater (a new one costs 35,000 won only at G-market (online retailers) and try to experiment. I'm pretty sure that your bill will be super low. Unlike many countries such as Pakistan, electricity is much cheaper than gas in Korea.
Another tip is: seal your windows with tape ( a duct tape or a regular scotch box sealing tape). It is very helpful in keeping the rooms warm. It took me a year to know this :-) I have learned all this the hard way (and the expensive way). I really do NOT want others to go through the same experiences that I did.
Last but not the least, get the good old 'hot water bag' which is being sold everywhere in stores.They are inexpensive and might ward off chills you will surely feel during the winters. I'm pretty sure that you will save not just the money but also will fight better to stay warm in winters.
Hence, try my tips and let me know how it worked for you?
I wish everyone a warmer winter this year around!