Most of the heaters we use are fan-heaters which blow out up to 3 or 4 kilowatts of heat. We also have some older heaters that will work with no electricity, and on which you can put a kettle or a pan of food. A friend in Sendai used some old ones after the earthquake when it was bitterly cold and there was no electricity. In situations like this, movable heaters make sense, as they need no infrastructure, and there are no gas pipes to leak. We have nine rooms in the house and four electric fan-heaters, so we can be flexible about which room we heat. Usually it's just the ones we're in. If we heat more of the house, we'll get through an 18 litre can every day.
To put that into carbon dioxide and into perspective, 18 litres of kerosene will release about 54 kg of CO2. It may seem strange that it can release more than its own weight in gas, but it just releases the carbon, which is the main constituent, somewhere between 6 and 16 atoms per molecule. Each carbon atom takes two oxygen atoms hostage from the atmosphere to make one carbon dioxide molecule. The lowest twenty CO2-producing countries emit less than 100 kg per capita per year, so in a couple of cold days with a couple of cans, we're well over our average, and that's before we've switched on the TV, done any cooking, or got into a car, bus or train. Average emissions in Japan are a hundred times this, at around 10 tonnes per person per year, very close to Germany, and about half the US.
It makes more sense to me to have a high level of insulation and keep the house warm the whole time. In spite of poor insulation levels, Japanese houses use very little fuel for heating. I think this is down to an idea "gaman" which translates fairly neatly into "keeping a stiff upper lip". People quite happily put up with cold, because it's good for them. This is a great thing in times of crisis, although I can't help feeling there are times when people need to stop putting up with hardship and make life better.
There seems to be a kind of wisdom in the philosophy of Japanese architecture that there's something wrong with a house if it doesn't reflect the outside temperature. If it's cold outside, it should be a little colder than normal inside, so that people are in touch with the seasons.This is ironic in a culture with such a strong sense of "inside" and "outside". Luckily there is no such sentiment regarding rain, as the same philosophy would mean that you should get slightly wet when it rains. Actually, I have heard many stories of newly-built houses leaking, but I'm sure that's not deliberate. There does seem to be a resistance to my quaint idea that houses should maintain a difference between the temperature inside and outside and it is not just a case of inability or incompetence. This is not just a matter of comfort; there are health consequences. Levels of stroke are much higher in Nagano Prefecture than in Hokkaido. Hokkaido is colder, but insulation is standard, and the temperature inside is much higher. Nagano is still one of the coldest parts of Japan, but only 18% of new houses meet the "next generation" energy standards, which correspond to European energy standards a couple of generations ago...
