The kotatsu (炬 燵) is the wooden frame of a low table, above which is placed a futon or heavy blanket.
Above the blanket is present a supporting surface to allow use as a normal table, while on the underside of the frame is mounted a heat source (typically an electric heater).
Kotatsu are used almost exclusively in Japan.
The history of kotatsu begins in Muromachi period (corresponding to the fourteenth century).its origins come from the traditional Japanese cooking system known as irori, which includes a fireplace located in the middle of a room covered tatami.
From the fourteenth century, it was introduced a session around all'irori, separating its functions of cooking food to those of a meeting place for family members.
In addition to a wooden structure located above all'irori it was put a quilt (called oki) This trapped and localized heat from the brazier under the structure. This primordial ancestor was called kotatsu Horigotatsu. The Japanese word Horigotatsu (掘 り 炬 燵) resulting from the union of kanji 掘 - り (ditch, well), 炬 (torch or fire), and 燵 (heat).
The realization of 'horigatsu It was slightly modified Edo period, in the seventeenth century. These changes considered the ground around all 'irori, where he began to make a square-shaped hole around the brazier.
The wooden structure horigatsu It was placed around this hole, forming a fireplace. The blanket was placed always on the structure, creating a warm place where he could get their legs in a sitting position.
The mobile kotatsu were created later on the concept of horigatsu, and spread by the shared use of tatami mats in Japanese homes.
The embers were no longer placed inside the 'irori but inside a jug pot that was placed on the floor; in this way it was possible to position the kotatsu where he wanted. this model kotatsu It is known as okigotasu.
In the Japanese word okigotatsu (置 き 炬 燵) comes from the union of kanji 置 き (place), 炬 (torch or fire), and 燵 (heating).
In the mid-twentieth century electricity replaced coal as the source of heating, and it was possible to attach an electric resistance to the kotatsu structure instead of using the clay brazier.
In this way, it became easier to move kotatsu at will, and this contributed to its spread in Japanese homes.
The modern model of kotatsu (oki-gotatsu (置 き 炬 燵?)) It consists of the frame of a table, on the underside of which an electric heater is fixed. The heat source is, as already said, an evolution of the traditional clay pot in which the embers were placed.
In the structure of the kotatsu It is usually slightly futon or blanket. A second futon (heavy) is placed on top of the kotatsu, and above that it is placed on the surface of the table. The electric resistance attached to the underside of the table heats the space under the blankets.
The most traditional type of kotatsu consists of a table arranged above a pit dug in the ground and in depth of about 40 centimeters (Hori-gotatsu (掘 り 炬 燵?)). A hotter coal is placed in the floor of the pit, along its walls or, as in the case of modern kotatsu, attached to the frame of the table.Some kotatsu Pit are also equipped with an electric resistance.
To this day the kotatsu is formed by an electric resistance fixed to the table frame, which can be made as well as traditional wood also with plastic or other materials.
Usually a cover is draped around the frame under the table. This cover is covered by a second heavier cover called the kotatsugake (火 燵 掛 布?).
The Kotatasugake often, they have a decorative function, and can be designed to match the furnishings of the house. To warm you sitting on the floor or on the zabuton, put his legs under the table with the lower body wrapped by kotatsugake.
The kotatsu was designed with traditional Japanese clothing in mind that allows the heat to enter the bottom of the clothes and exit the neck, allowing them to warm the whole body.
Most Japanese houses are not insulated effectively like those in the West and are not equipped with central heating systems to heat the various rooms. Heating the house is very expensive, as well as insufficient thermal insulation for exposure to drafty apartments.
The use of kotatsu It allows a relatively inexpensive source of heat to trust during the winter months, taking into account that the futons can retain warm air.
Families can choose to focus their activities in the room where it is placed kotatsu to save on energy costs. During the summer season, the cover is removed and kotatsu can be used as a normal table.
You can sleep under kotatsu, although normally a person's body (unless it is very weak) is not completely covered by the futon. Sleeping under the kotatsu It is considered acceptable for naps, but it is ideal for night rest for several reasons: the body is not completely covered and heated in a non-uniform; the table is short and it is possible to accidentally touch the moving heating elements while sleeping, exposing oneself to the risk of sunburn.
Children have said that if they sleep under kotatsu get a cold; however, it is often the case that animals (such as cats) sleep under the kotatsu be able to be with their whole body inside the cover - in a way similar to cats who sleep next to underfloor heating vents in Western countries (Japanese homes are not this type of heating).
During the winter months in Japan kotatsu It is often the center of family life. In the evening, families gather around the kotatsu to eat, watch TV, play games and cat to keep your legs warm under the kotatsu.
While kotatsu had its golden age in the late 1970s, its production declined afterwards, as it failed to find its place in the face of the underfloor heating and air-conditioning systems found in modern Japanese homes. However, the kotatsu allows significant energy savings.
The blanket on the table keeps the heat within a defined area. The electricity consumption of a kotatsu is only half that of an air conditioner that heats an entire room.
With energy concerns on the rise since the March 2011 earthquake, sales of kotatsu have been on the rise again. While kotatsu is once again popular for its economic benefits, it is above all an invitation to socialize with others over a steaming cup of tea, always warm.