The kang (炕) is a traditional heated platform, 2 metres or more long, used for general living, working, entertaining and sleeping in the northern part of China, where the winter climate is cold. It is made of bricks or other forms of fired clay and more recently of concrete in some locations.
Sites in Shenyang, Liaoning in Northeast China show humans using heated bed floors as early as 7,200 years ago. Other examples include an unearthed 1st-century building remains in Heilongjiang Province, and another one in a 4th-century palace building in Jilin Province, both also in the Northeast region. Literary evidence from Li Daoyuan's “Commentary on the Water Classic” also gives evidence of heated floors during the Northern Wei Dynasty (386–534 AD).
The kang is used to cook meals and heat the room, producing radiant heat to indirectly warm the interior space as well as the bed mass itself. It has been speculated that one of the oldest forms of Chinese housing, cave dwellings known as yaodong (窰洞), widespread throughout northern China would have been uninhabitable without the kang. https://www.tumblr.com/sinoheritage/775197346221916160/yaodong-%E7%AA%B0-in-native-jin-chinese-or-%E7%AA%B0%E6%B4%9E-in
