Ondol Summary
Ondol is a traditional Korean house heating method. It is also called Banggudeul.
Heating method is make a fire at the fuel hole, and heating is done when hot smoke contained heat which was generated at the fuel hole passes through the Gudeuljang(room floor), and the said smoke is gone out into the chimney at the end of the Gudeuljang.
A typical device of similar concept with Ondol is Hypocaust which is a Roman era's large bathhouse warm water supply method of primitive type (only comprised of fuel hole and Gorae) that Bulmok(the warmest part of the heated floor) or Gaejari is none. Furthermore we can also take a Gloria which was used for heating device of medieval castle that was derived from Hypocaust.
Heat Method around the world
Hearth of West and Irori of Japan and so on are the heating apparatus directly using the heat source, while Ondol has a feature that use the generated 'indirect radiant heat' warming up the Gudeuljang and Gorae under the Gudeuljang by the heat.
That's why if a certain Gudeuljang was well made, heat of the Gudeuljang relatively keeps up for long time even if got rid of the direct heat source from the fuel hole. Condition of the good Gudeuljang depends on how long this 'remaining warmth' would be lasting.
Demerit is that once Gudeul (room floor) is split or broken, smoke comes up and carbon monoxide poisoning could be happened.
As problem of the heat efficiency can be taken, it tends to heat excessively beyond necessity to pass overnight with the remaining warmth after making a fire before sleeping. Another demerit is that temperature difference between the place on the Ondol floor nearest the fireplace and the upper side of the floor away from the fireplace is occurred under the structure of Ondol.
