The history of the kotatsu begins in the Muromachi period or Ashikaga shogunate during the fourteenth century. Its origins begin with the Japanese cooking hearth, known as the irori. Charcoal was the primary method of cooking and heating in the traditional Japanese household and was used to heat the irori. By the fourteenth century in Japan, a seating platform was introduced to the irori and its cooking function became separated from its seating function. On top of the wooden platform a quilt was placed, known as an oki that trapped and localized the heat of the charcoal burner. This early ancestor to the modern kotatsu was called a hori-gotatsu. The word hori-gotatsu (掘り炬燵) is derived from the kanji 掘り (hori) meaning ditch, digging, 炬 (ko) meaning torch or fire, and 燵 (tatsu) meaning foot warmer.
In the twenty-first century, the kotatsu typically consists of the electric heater attached to the frame, which is no longer limited to wood, but may be made of plastic or other materials. Generally, a blanket (or shitagake) is draped over the frame and heater and under the table-top. This first blanket is covered by a second heavier blanket, known as a kotatsu-gake (火燵掛布). Kotatsu-gake often are decorative and may be designed to match home décor. A person sits on the floor or on zabuton cushions with their legs under the table and the blanket draped over the lower body. The kotatsu was designed when people most commonly wore traditional Japanese style clothes, where the heat would enter through the bottom of the robes and rise to exit around the neck, thus heating the entire body.
Most Japanese housing is not insulated to the same degree as a Western domicile and does not have central heating, thus relying primarily on space heating. Heating is expensive because of the lack of insulation and the draftiness of housing. A kotatsu is a relatively inexpensive way to stay warm in the winter, as the futons trap the warm air. Families may choose to concentrate their activity in this one area of the house in order to save on energy costs. In the summer, the blanket may be removed, and the kotatsu used as a normal table.
During the winter months in Japan, the kotatsu often is the center of domestic life. In the evening family members gather around the kotatsu to enjoy food, television, games, and conversation whilPost too long. Click here to view the full text.