According to the results of the relevant studies, it is thought that the form of underfloor heating system (oejulgudeul) used in houses in the central region of the Korean Peninsula during the Proto-Three Kingdoms Period changed from the “ㄱ”-shaped system installed near the rear wall of a room (“A” type) to the “ㄱ”-shaped system installed near the side wall of a room (“B” type), and then again to the ‘-’-shaped (“C” type) system. Until recently, most researchers thought that each type of system emerged and developed under the influence of external factors, such as a specific polity, but excavation surveys have provided the basis by which the haphazard changes in each type of heating system can be confirmed typologically, while other recent studies have criticized any political interpretation of the types of heating systems.
Recently, two controversies have arisen among researchers about the underfloor heating systems. Although most researchers agree that the heating system originated from the Duanjie-Krounovka culture, they are divided in their views about its development after the settlement of the central region of the Korean Peninsula. Some researchers believe that the heating system gradually developed amid climatic changes and the growing need to use a residential space, while others think that each of the three types was adopted from a different source and at a different time.
This study reestablishes their classification, establishes stages of development, and reviews the process of change based on their temporal order relation in accordance with existing chronological records, and examines their distribution patterns in different regions. The results of the study show that the heating system changed from the “A” type to the “B” and then “C” types. As regards those that deviated from the standardized form among the “A” type systems, this study categorizes them and examines how they changed over time.
At first, the heating system in question was distributed only in areas along the upper reaches of the Bukhangang River; and many more houses used a charcoal stove than an underfloor heating system. Later, however, the heating system gradually disappeared from this area, and instead came to be used in areas along the upper reaches of the Imjingang and Hantangang Rivers and in the midstream area of the Hangang River to the east of the Pungnaptoseong Earthen Fortification. In these areas, the “A” type of heating system gradually disappeared to be replaced by the “B” and “C” types, after which the latter gradually spread to most of the areas along the Hangang River. Thus, it is difficult to accept the view that other types of heating system were gradually adopted after those that spread from the Northeastern region of the Korean Peninsula settled in the central region or that each type developed independently from each other.