Kotatsu and Staying Warm in a Japanese Home: Words and Tips

Staying warm in four phrases

These four lines cover most winter conversations at home. The first is a national joke: the kotatsu is so warm that nobody can get out. The others name the three most common ways people keep warm.

Why Japanese homes feel cold

Many Japanese houses were built for humid summers, with an emphasis on airflow rather than keeping heat in. Older buildings often have thin walls, single-glazed aluminium window frames and gaps around sliding doors. Insulation standards have improved a great deal, so a new flat can be warm, but a 30-year-old wooden house or a cheap rental can be very cold.

The habit that follows is to heat the room you are using. The living room is warm, the corridor and toilet are not, and the bathroom can be the coldest place of all. Many homes have a heated toilet seat for exactly this reason. Sudden temperature changes between a warm room and a cold bathroom are called heat shock (ヒートショック) in Japanese, and it is a common winter health topic on TV, especially for older people.

The kotatsu: Japan's favourite winter furniture

A kotatsu is a low table with an electric heater under the top. In autumn you bring out the quilt, the kotatsu buton (こたつ布団), lay it over the frame and put the tabletop back on. You sit on the floor with your legs under the quilt, and the warm air stays trapped there. It uses much less electricity than heating the whole room, which is why it survives even in homes with air conditioners.

The kotatsu is also a social space. Families eat dinner, play cards and watch New Year TV around it, and a bowl of mandarins, mikan, on top is the classic winter picture. The downside is famous: once you are in, you do not want to get out, and people fall asleep under it. Many people advise against sleeping in one all night, since your body dries out and it is easy to get dehydrated.

Air-con, kerosene and other heaters

Most flats have an air conditioner on the wall, the eakon (エアコン), which also heats. Heating mode is danbō (暖房), and in very cold weather it can struggle and run up a high bill. Many families add a kerosene heater: either a sekiyu sutōbu, which heats by radiant warmth, or a sekiyu fan hītā, which blows hot air. Kerosene, tōyu (灯油), is sold at petrol stations and by small delivery trucks that drive around neighbourhoods playing a recognisable tune.

Kerosene and gas heaters burn fuel inside the room, so they need fresh air. Many people open a window for a few minutes every hour, and manuals tell you to do so. Some rental buildings forbid them entirely. Electric options include oil-filled radiators, ceramic fan heaters and electric blankets, denki mōfu (電気毛布).

Kairo, yutanpo and dressing warm

The disposable heat pack, kairo (カイロ), is everywhere in winter: in convenience stores, pharmacies and 100-yen shops. There are pocket ones to hold and sticky ones, harukairo (貼るカイロ), to put on your clothes over your lower back or stomach. Do not stick them directly on skin, and follow the packet instructions.

The yutanpo (湯たんぽ) is a hot water bottle, often a hard plastic or metal one in a fleece cover, filled at night and put in the bed. Indoors, people wear layers and fleece, warm socks and slippers, and a padded jacket called a hanten (半纏) or dotera (どてら) is still loved in some homes.

Condensation, mould and talking to your landlord

When a warm, humid room meets a cold window, water runs down the glass. That is ketsuro (結露), and in a rental it quickly becomes black mould, kabi, on frames, curtains and the backs of wardrobes. Wipe the windows in the morning, air the room, run the bathroom fan and keep furniture slightly away from outside walls. If the problem is severe or something is broken, contact the landlord or management company, the kanri gaisha (管理会社), politely and early.

Electricity bill talk and a family dialogue

Heating bills are a favourite winter topic, and denkidai (電気代), the electricity bill, comes up at home, at work and in the news. In a family or share house, deciding when to switch the heater on is a small daily negotiation. Here is how it sounds in casual speech.

Tsukeppanashi means left on, from the verb plus ~ppanashi, leaving something in a state. You will also hear denki no tsukeppanashi, leaving the lights on, and mado no akeppanashi, leaving the window open.