February 2025 | The Wonderful Kotatsu 1
The Wonderful Kotatsu
A symbol of Japanese innovation
Description
A kotatsu is a low, wooden table frame covered by a futon, or heavy
blanket, upon which a table top sits. Underneath is a heat source,
formerly a charcoal brazier but now electric, oen built into the table
itself.[1] Kotatsu are used almost exclusively in Japan, although similar
devices for the same purpose of heating are used elsewhere, e.g. the
Spanish brasero or Iranian korsi.
History
e 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 Jap-
anese 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. is early
ancestor to the modern kotatsu was called a hori-gotatsu.
e formation of the hori-gotatsu was slightly changed in the Edo
period during the seventeenth century. ese changes consisted of
the oor around the irori being dug-out into the ground in a square
shape. e wooden platform was placed around this, making a
hearth. en the blanket was placed on top of the platform again,
where one could sit with legs underneath to stay warm.
An Edo-period kotatsu at the Fukagawa Edo Museum.
Diagram of an electric and charcoal kotatsu.
A kotatsu in a modern Japanese home.
2 The Wonderful Kotatsu | February 2025
History (cont.)
e moveable kotatsu was created later, originating from the
concept of hori-gotatsu. is kotatsu came about with the
popular use of tatami matting in Japanese homes. Instead
of placing the charcoals in the irori, they were placed in an
earthen pot which was placed on the tatami making the ko-
tatsu transportable. is more modern style kotatsu is known
as the oki-gotatsu.
In the middle of the twentieth-century charcoal was replaced
with electricity as a heating source. Instead of having the
moveable earthen pot of charcoals beneath the kotatsu, it was
possible to attach an electric heating xture directly to the
frame of the kotatsu. By 1997, the majority (approximately
two-thirds) of Japanese homes had the modern irori and 81
percent had a kotatsu, though they are warmed using elec-
tricity instead of glowing coals or charcoal. us, the kotatsu
became completely mobile with electricity and became a
common feature of Japanese homes during winter.
A tatami mat covering the oor of a Japanese home.
Types
ere are two kinds of kotatsu used in Japan today, diering in the
conguration and the type of heating:
Electric
e modern style of kotatsu, oki-gotatsu, consists of a table with
an electric heater attached to the underside of the table. is
evolved from a clay pot with hot coals placed under a table.[2] e
kotatsu usually is set on a thin futon, like a throw rug. A second,
thicker blanket is placed over the kotatsu table, above which the
tabletop is placed. e electric heater attached to the underside of
the table heats the space under the comforter.
Charcoal
e more traditional type is a table placed over a recessed oor,
hori-gotatsu. e pit is cut into the oor and is about 40 centi-
meters deep. A charcoal heater is placed somewhere in the pit’s
oor, walls, or, as in the modern-style kotatsu, attached to the
table-frame. ere are pit-type kotatsu with an electric heater too.
An electric kotatsu on its side.
Coal briquettes used in the early 20th century.
February 2025 | The Wonderful Kotatsu 3
Functionality
In the twenty-rst 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. is rst blanket is covered by a second heavi-
er blanket, known as a kotatsu-gake. A person sits on the oor or on zabuton cushions with their legs under
the table and the blanket draped over the lower body. e kotatsu was designed when people most com-
monly 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 drainess of housing.
A kotatsu is a relatively inex-
pensive 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.
A Japanese man seated at a kotatsu.
It is possible to sleep under a kotatsu, although unless one is quite short, one’s body will not be completely
covered. is generally is considered acceptable for naps, but not for overnight sleeping for many reasons:
one’s body is not completely covered, yielding uneven heating; the table is low, so one may touch heating
elements accidentally when moving while asleep, risking burns. Traditionally, children are told that they
will catch a cold if they sleep under a kotatsu. Pets such as cats
frequently sleep under kotatsu, however, and are small enough
to t completely underneath—comparable to cats who sleep on
oor heating vents in Western countries (Japanese homes do not
generally have oor heating vents).
During the winter months in Japan, the kotatsu oen is the
center of domestic life. In the evening family members gather
around the kotatsu to enjoy food, television, games, and conver-
sation while keeping the lower half of their bodies warm. It has
been said that “once under the kotatsu, all of your worries slip
away as a familiar warmth takes over and you become completely
r e l a x e d .”
Historically, kotatsu-gake were made of bast bers. Later, cotton was introduced (1300s to 1700s, depending
on region) and they were usually made of bast-lled quilts of recycled cotton, dyed with indigo and pieced
from old garments in boroboro style. Kotatsushiki, for going under the kotatsu, as a oor covering, were
made the same way. In the 2010s, kotatsu-gake were oen decorative and might be designed to match home
décor.
A Japanese woman resting beneath a kotatsu.
4 The Wonderful Kotatsu | February 2025
In Other Countries
ere are similar economical and oen sociable systems to keep
warm while sitting still in countries around the world.
Europe
In Spain and Portugal, the mesa camilla [es] is a small round
table with a brasero heater (i.e. a brazier) placed underneath. e
Netherlands used to use a foot stove. During World War I, British
Royal Engineers built ‘Japanese footwarmers’ in the trenches. e
18th-century traveler Lady Mary Wortley Montagu describes the
similar tendour in her Turkish Embassy Letters.
e Middle East
Tajikistan and Afghanistan have the very similar sandali, used even
today in many traditional houses as a warm family eating place.
Another similar item called the korsi is used likewise in Iran.
East Asia
In China and Korea, underoor heating traditionally is used. e
devices used in a similar fashion are, respectively, a Kang bed-stove
and an ondol. Romans used a hypocaust for underoor heating.
A Dutch foot stove.
A korsi, found in Afganistan and Iran. Note the
similarity to the kotatsu.
A family of four eating a meal on a kotatsu.
Summary
All in all, kotatsu have a number of benets. e typical kotatsu
(Okigotatsu) uses between 500-600W of electricity, with some us-
ing as little as 70W. Compared to the typical wall unit heater, which
can easily run at over 1500W, the kotatsu runs at much less energy.
Moreover, because the kotatsu heats only a small space, with the
hot air being contained by a blanket, little heat is lost. Additionally,
dust and allergens are not emitted, resulting in improved indoor
air quality.
Some of the best benets, however, are the
kotatsu’s secondary function – a gathering spot
for families and friends. Much like a campre in
the summer, the kotatsu provides a warm place for
gathering, whether for dining or just relaxing. In
fact, their warmth and comfort oen makes them
dicult to leave.
Information obtained from Wikipedia.com.
