Keep Warm With a Kotatsu

 Winters can be harsh. With the strong winds and freezing temperatures, going outside is hardly an option during this season. With so little to do but brace the cold months, the Japanese people have invented a way to keep warm in a comfortable way. The kotatsu is Japan’s solution to the problems most families encounter during the winter season.

The Magic of a Kotatsu Heater

A kotatsu is a Japanese appliance that is widely used during the winter season. It is often the point of gathering for Japanese families during the winter months.  This heating appliance typically consists of a table, a futon, and a source of heat. The kotatsu table is basically a regular wooden table with space or compartment underneath for the heat source. The futon, the Japanese equivalent of a really thick blanket, coverlet, or quilt, is laid over the kotatsu table. These are the three core items that make up a kotatsu set.

By Sjschen (Own work) [CC BY-SA 3.0 or GFDL], via Wikimedia Commons

The warmth that is emitted from the heat source is trapped under the thick fibers of the futon. This provides a warm, comfortable, and relaxing haven against the low temperatures of the summer season. Typically, people place only the lower half of their bodies under the futon. It is not recommended to sleep while seated under the futon of the kotatsu because accidentally touching the heat source will cause your skin to burn. Japanese families often gather around the kotatsu, with their lower bodies under the quilt, and use the table to either eat, drink, watch tv, or play games. It is a custom for Japanese families to eat mandarins while gathered around the kotatsu during the winter, which typically occurs starting late-November up till early-February.

The History Behind the Kotatsu

Believe it or not, the history behind this ingenious source for warmth and social gathering started in the 14th century, during the Muromachi era. Historically speaking, the kotatsu started out as the traditional Japanese fireplace. This was known as the irori and was primarily used for cooking meals. The source of heat used to fire up the irori was charcoal. Typically the irori was built in the middle of the room and the Japanese would sit around it.

Photo by Marieve 瑞香 Inoue

It was during the Muromachi era that more and more Japanese households started introducing a seating platform to the irori setup. This separated the use of the cooking heart’s function into seating and cooking. Soon after a quilt, called an oki, was placed on top of the wooden platform of the irori. This quilt trapped the heat that was being emitted by the charcoal in the irori. Called the hori-gotatsu, this was the earliest form of the modern day kotatsu. The name hori-gotatsu was derived from three kanji words; hori, ko, and tatsu. Hori is a term that used to describe a ditch or the act of digging. Ko is the term used to describe a torch or flame. Tatsu is the term used to describe a foot warmer.

The hori-gotatsu was widely used up until the 17th century, during the Edo period. This was when changes to the old setup were introduced. The first change done to the irori that was introduced was the digging of the surrounding floor. A wooden platform was then placed around this. This allowed one’s legs to hang as if sitting on a chair. A blanked was then placed on top of the platform which provided warmth for those that put their legs under. This was the concept used for the kotatsu up till now because it was designed for the use of people wearing traditional Japanese clothing. Traditional Japanese clothing would often have loose pants or dresses. The heat would enter the bottom of their clothing and would exit by the lapel and sleeves, allowing the heat to spread throughout the body.

The modern day movable kotatsu was created later alongside the rise of popularity in the use of tatami mat flooring used in Japanese homes. This new form of heating, called the oki-gotatsu,  was based on the concept of the hori-gotatsu. The oki-gotatsu got its name from three kanji words; Oki (which means placement)  ko, and tatsu.What changed was the placement of the heating source. Where the hori-gotatsu would involve charcoal being placed directly in the irori, the oki-gotatsu would be stored in an earthen pot that was placed on the tatami mat.

It was in the middle of the 20th century that electricity was introduced to the kotatsu setup. Charcoal was replaced with electricity as being the heat source. The moveable earthen pot storing the charcoal was replaced by modern day electric heating fixtures that could be attached directly to the frame of the kotatsu. This is the form known by many as the modern day kotatsu, with the frame, blanket, and heat source being completely mobile.

The 21st-century version of the kotatsu has undergone minor changes to accommodate the modern Japanese family and home. The frame, from which the heat source is directly attached to, is now made of materials other than wood, such as plastic. The blanket, from which the heat is trapped and localized underneath, is now separated into two, a shitagake and a kotatsu-gake. The shitagake blanket is first placed over the kotatsu frame and heater, while the kotatsu-gake is placed over it. The kotatsu-gake is much heavier and thicker than the shitagake blanket. Since the kotatsu-gake is visible from the outside, it is often laid with intricate patterns and is often bought to match the home decor. Japanese families typically sit on the floor or on cushions called zabuton. Their legs are then spread under the table and the blanket is used to cover the lower body.

Japanese homes are not built in the same way that western homes are built. Japanese homes often prioritize airflow and insulation are not as intensive. Central heating is also not common in Japan thus the use of a kotatsu provided Japanese families with a way to keep warm in an economical way. This also allowed for families to spend more time together as activities were centered around the use of the kotatsu. Also, the kotatsu does not lose its purpose during the rest of the year as the blanket and heating unit can be removed. The kotatsu table is then used as a normal table.

Sleeping Under a Kotatsu is Not Recommended, Unless You are a Cat

As mentioned earlier, sleeping under a kotatsu is not recommended but is entirely possible. Generally, Japanese people sleep under the kotatsu only when taking short naps. Sleeping overnight under the warmth of a kotatsu might be tempting when the temperature outside is below zero, but it is not acceptable for many different reasons. Unless the person is of shorter stature, his or her body will not be kept completely warm, leaving the upper part of the body susceptible to the cold. The kotatsu table is typically built to be low in height, much like a coffee table. This raises the chances that one might touch the heating source when changing sleeping position or fidgeting. This could cause burns to occur on one’s skin. It is a common saying that children should not sleep under a kotatsu as this could cause them to catch a cold. Babies and toddlers should not be kept under the kotatsu. They might not have the strength or wisdom to get out of the kotatsu. It is not hard to imagine a baby getting trapped underneath the heavy futon. The heat from the kotatsu will seriously dehydrate the baby and could cause serious or fatal illness.  

Pets, most commonly cats, frequently sleep under the kotatsu as they are small enough to completely fit underneath it. This is something comparable to domestic cats sleeping on the heating vents in western countries.

Photo by Justin Doub

The Different Forms of A Kotatsu: Table, Sofa, Futon, and Couch

In the modern day and age, the Japanese homes have taken in more western influences. More and more Japanese families have started to use high chairs, tables, and sofas. This has led for the redesigning of kotatsu to fit the needs of the new Japanese home. Now manufacturers make products in different shapes and heights. There are kotatsu that are made to be placed near sofas and chairs. Their heights are the prime heating appliance for the modern Japanese homes who still wish to stay warm the traditional way. Aside from the use of shitagake and kotatsu-gake, some families opt to use western comforters as they are large enough to be placed on the table and can still trap heat underneath.

Regardless of the height of the table and the blanket used, the two main types of kotatsu used in Japan today are in reference to its heat source, electric and charcoal. The electric kotatsu, or modern style kotatsu, is a table with a heat source, powered by electricity, attached underneath. This kotatsu uses the shitagake and kotatsu-gake setup for trapping heat. The second type of kotatsu,  the charcoal or traditional kotatsu, is a table placed over a dugout floor or pit. The depth of the pit is typically 40 cm deep. A charcoal heater, or even a traditional earthen pot, is placed in the middle of the pit’s floor, the walls surrounding the pit, or the kotatsu table. There are some manufacturers that make traditional kotatsu with an electric heater.

DIY Tips for Making Your Own Kotatsu

It might be a good woodworking and electrical project for someone to try and build their own kotatsu. It is a very simple thing to do when you think about it. Just build a standard table and adjust the heights of the legs to one’s preference. Then buy, or even knit if you are up to the task, a thick quilt that will act as a futon. The last would be a heat source. One may opt to buy a separate kotatsu heater, which is sold on their own or build your own using a heating or halogen lamp. It is suggested to buy a heater as the fire hazards involved in building your own heater is too great for those who do not know what they are doing. One may also opt to create a more traditional kotatsu by creating a pit for the heater to be placed. It is suggested to dig the pit at least 40 cm deep, one meter wide, and one meter long.

Sites That Have Kotatsu For Sale

The best place to purchase a kotatsu online would have to be at Rakuten Global Market. On this site, one may purchase a variety of Japanese products, including different types of kotatsu. Rakuten Global Market sells the kotatsu at around 100 US Dollars. This is a full kotatsu set which includes a table, futon, and electric heating source. The trend for futons now is it being made with the use of microfiber but more traditional futons may be purchased as well.

Another site to buy kotatsu sets would be  A full kotatsu set on Amazon can cost anywhere between 150 US Dollars up to 300 US Dollars. The sets found here are all manufactured in Japan so it won’t come as a surprise to find the same set on both sites. It is recommended to fully read the item description when buying these sets as to ensure that the voltage setting is applicable to one’s home. Both the US and Japan use the same voltage of 120V. For those countries that typically use 230V or greater, plugging in the kotatsu will only fry the electrical parts.

It is during the winter season that most Japanese families gather around the kotatsu. It is undoubtedly the center of their domestic life during this season. From enjoying food together to watching television, the kotatsu provides Japanese families with an area to sit back, stay warm, and socialize. It is a common saying that once a person goes under a kotatsu, all their troubles fade away. Warmth and relaxation from this wondrous invention take over everyone who sits underneath it.