Central heating usually means using one heating system or heat source to warm several rooms throughout a home. In much of Japan, however, it has long been more common to heat individual rooms instead, such as the living room or bedroom being used at the time.
For some Japanese people, the question “Why don’t you heat the whole house?” may not even have occurred to them. In winter, the living room is warm, the bedroom may have a separate heater, and the hallway or changing area can still be cold. In many parts of Japan, that kind of home environment was never especially unusual.
Part of the reason is climate. Much of Japan has winters, but many regions are not as severely cold as places such as Hokkaido, where keeping the entire home warm is much more important. Japanese houses also had to deal with hot, humid summers. Many older homes were built with ventilation and airflow in mind, rather than with the single goal of keeping heat sealed inside.
At the same time, room-by-room heating was easy to arrange. Air conditioners, kerosene heaters, and kotatsu could warm the space people were actually using. Heating empty rooms and hallways could simply feel wasteful.
Japanese people are not especially attached to cold houses. If the cost were about the same, many people would probably rather have the whole home comfortably warm. Room-by-room heating was less a cultural preference than a practical habit that worked for a long time.
Housing standards are changing. Insulation is now given much more attention, and older homes can be upgraded by improving windows, walls, floors, and ceilings. Government programs also support energy-efficiency renovations, so the performance of the house itself is increasingly becoming part of the solution.
For people who grew up with room-by-room heating, even a cold hallway in winter did not necessarily seem strange. Heating only the rooms in use simply felt normal, so there was little reason to wonder why the rest of the house was cold.