The idea of the kotatsu is based on two quintessentially Japanese principles. The first is the metaphysical idea of keeping a positive energy flow (qi*) in the body by keeping the top half of the body cool, while the bottom half is nice and warm.. The second is trying to reach maximum efficiency in this case by only heating the area where you actually are, rather than the whole house or apartment.
So what is it? The kotatsu is essentially a low table with a small heater underneath. The original incarnation of the kotatsu in the 14th Century used charcoal, but today the heater unit is a small, cheap, and electric and screws into what looks like a normal coffee table. The heater, legs and table frame are covered with a heavy blanket to keep the warm air in, and a tabletop fits over the blanket to give a more useable, and spillproof, surface. Every home improvement store in Japan sells Kotatsu, but they’re hard to find in the US at a reasonable price, but there are a good DYI instructions out there.
As the picture above shows, it’s low to the ground and meant to be used by one or two people when sitting on the ground, or leaning against the wall, the way Japanese usually sit when lounging around the house. If it was to be adopted in the chair-based cultures, the legs and blanket would have to be lengthened, which would lower efficiency a little, but the basic design concept would still be the same, and is in fact sold on the Rakuten (Japan’s alternative to Amazon).
Without a massive rise in home heating costs, it’s hard to see the Kotatsu really taking off as a home heating solution. But even more than the product itself, I respect the underlying thinking behind the kotatsu: using only what you what you need, where you need it, and when you need it. The ice pack bra? Not so much.
*’qi’ is a legit English scrabble word. You’re welcome.
[Images by panina. anna under CC]