I must admit a complete fascination with Japan, generally with the refinement and strangeness of its culture of course, and especially with its traditional understanding of domestic thermal comfort. It is surprising that their traditional culture is not that dissimilar to ours regarding thermal comfort. Our current expectations of an eternal spring indoors is less than 50 years old. And really this is a luxury that we cannot afford any longer.
Although a much hotter and humid climate in the summer, the Japanese winters are not that dissimilar to the oceanic climate of Western Europe; snow is not unusual in the winter. The traditional Japanese home is entirely uninsulated - a timber frame infilled with lightweight and thin panels (some fixed, others sliding). The only fixed heating appliance is formed by an earth placed (Irori) in the middle of the kitchen, the space of the rest of the house is not heated.
A study by Arianna Sdei (The Martin Centre for architectural and urban studies, Cambridge University, Cambridge UK) has shown that the internal daytime temperature in the colder days is just above 14 degree C. This temperature, as I experience every winter in our uninsulated and draughty warehouse, is comfortable as long as you wear multiple layers and use localised and radiant heating. This is not that dissimilar to the way we used to live in Western Europe - as my grandmother tells me and I experienced as a child - we used to wear more and warmer clothes in cold interiors warming ourselves up near fireplaces and preparing beds with bed warmers.
And this is exactly what the Japenese did, they wore multiple layers of clothing and blankets. These were warmed up with up bed-warmers and small lacquered boxes placed in sleeves to warm ones hands.
Movable heating elements offer localised radiant heating, either small charcoal brazier (Hibachi) or by a piece of furniture called kotatsu. This is a low table with a heating element on the bottom. During cold weather, people sit around the table and keep the heat contained with a light duvet-type cover that surrounds the table. This table is used for work and dinner. It used to be placed over a hole in the floor. These can be seen as movable fireplaces that do not require chimneys as they use smokeless charcoal.
It is worth pointing out that there is a cultural aspect to the idea of not heating a whole building. In Japan, it is considered wasteful (mottainai) for both one’s money and the environment.
This understanding of wastefulness as a negative that should be avoided is something that we should learn from, or I should say re-learn. We do not need to heat spaces when we could just wear more clothes. Of course, we should insulate our buildings well so that they are warmer than Japanese and European homes of the past but we simply should not use central heating.