The Korean Ondol Heating System

The term gudeul comes from the Korean language. According to Korean folklorist Son Jintae, the word gudeul comes from the Korean word guun-dol, which means “heated stone,” and has been pronounced as gudol, gudul, and then gudeul. The Sino-Korean term ondol was first used at the end of the nineteenth century. Janggaeng, hwagaeng nandol, and yeondol are all names for the same thing.

Right under your feet is one of the most energy-efficient ways to heat your homes. For millennia, Koreans have kept warm by cooking with the least amount of fuel possible while also heating their homes. When the fire used for cooking is repurposed for heating the house, the “Ondol,” an elevated indoor floor, is heated.

Thermal energy from cooking or heating the room is transferred upward as heat rises from the underfloor, warming up the stone slabs and gradually releasing the thermal energy, in other words, air convection is used to maintain a warm temperature. You may also read the guide to traditional Korean homes styles to explore these forms of mechanism that have kept Koreans warm through the pangs of the winter season.

The Origin of Ondol

Ondol is thought to have originated in the Bronze Age (900 BC-800 BC) and evolved into the features we enjoy today during the Three Kingdoms of Korea (57 BC-668 AD). This is an estimate based on artifacts built between 200 BC and 0 BC, indicating widespread use of brick and stone ondol across the Korean peninsula. It’s widely assumed that the system was created to control the flow of smoke from fireplaces rather than attempting to use the fire itself as a source of direct heat, as most Western heating systems do.

Archaeological sites in modern-day North Korea have discovered ondol use. In the excavated dwelling of a Neolithic Age archaeological site discovered in Unggi, Hamgyeongbuk-do, in present-day North Korea, a clear vestige of gudeul can be seen. Early ondols were gudeul, which provided heating and cooking for a home. Because the flue entry was beside the furnace, when a fire was lit in the furnace to cook rice for dinner, the flame would extend horizontally. This arrangement was necessary because the smoke could not travel upward, causing the flame to go out too quickly.

Uses of Ondol

Before the 1960s, the majority of Korean homes used the ondol as a living area for sitting, eating, sleeping, and other activities. The furnace burned mostly rice paddy straws, agricultural crop waste, biomass, or any type of dried firewood because Koreans are used to sitting and sleeping on the ground and working at low tables without chairs rather than raised ones. Rice paddy straws or crop waste were preferred for short-term cooking while longer cooking times and floor heating required longer-burning firewood. In contrast to modern water heaters, the fuel was either intermittently or consistently burned two to five times per day, depending on how often people cooked and the season.

The floor closest to the furnace would typically be warm enough under the old ondol heating, with the warmest spots reserved for elders and distinguished visitors. Environmental pollution and carbon monoxide poisoning from burning coal briquettes were issued in Ondol. Thus, modern Korean homes are heated by other technologies.

Frank Lloyd Wright, a well-known American architect, was invited to a Japanese family’s home while he was working on a hotel in Japan. The owner constructed an ondol room in his home after experiencing the ondol in Korea. Wright reportedly was so moved by the experience that he came up with radiant floor heating, a heating system that uses hot water. This system was used in a few of Wright’s structures.

Modern homes, such as high-rise apartments, have a modernized ondol system instead of ondol-hydronic radiant floor heating. Many architects use ondol in contemporary homes because they are aware of its advantages and benefits. Ondol is starting to be recognized as one of the home heating systems as it has been introduced to many nations. The ondol of today is not the same as the original. It is challenging to find the conventional ondol system in Korean homes because almost all Koreans use modern equivalents. To survive the harsh winters, North Korea continues to use the fundamentally traditional Ondol design, which relies primarily on coal rather than biomass. There are other heating tips for winter that are suggested for varied locations but uniquely enough, Korea historically designed their own style of coping with the challenging weather of their geographical location.

Ondol Benefits

Traditional homes benefited further from the ondol heating system. Rats and insects couldn’t live underneath the houses because of the gorae that ran beneath them and was constantly channeling hot smoke. Small amounts of smoke that escaped the channel through the ground served as pest control, keeping bugs away from garden trees and preventing ants from damaging the wooden structure of the house during the winter.

Additionally, Koreans received a number of health advantages from heating the floor. The air in the room naturally circulated because the air heated by the hot floor moved upward and the cold air moved downward, in accordance with the law of thermos dynamics. People slept on the floor, which caused the heat to increase blood flow to their legs and backs. Some even assert that ondol systems are very similar to Finnish saunas and Japanese hot springs in terms of their ability to help people withstand long winters and offer the same health benefits.

Korean fireplace in the kitchen

The Korean hanok, or traditional house, begins by heating the kitchen using a traditional Korean fireplace. The “ondol” underfloor heating system helps Koreans endure their long, bitter winters. A global marketing campaign is currently in progress to promote ondol, which has a history dating back to the Neolithic era. This traditional Korean heating system offers several health benefits. The heated floor provides warmth to the body especially the back and the feet allowing blood circulation in the body which results in positive health results.