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Comment by laurieg | Hacker News Reader

Unfortunately Japanese buildings tend to be optimized for airflow (people want buildings that don't get mouldy). Also many of them are not well insulated (double pane windows are still a rare luxury) so buildings don't retain the cold air well.

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Optimized for airflow is true for traditional Japanese buildings, but recent decades buildings are just poorly made for insulating and also not optimized for airflow, because builders and regulations were lazy. It was really stupid poor regulation because Japan imports all energy source.

Also it is not like they were not capable of making them to proper standards. As in Northern parts it is entirely comparable to North European levels of insulation and quality... Japan is weird country sometimes...

Thermal insualation decreases mold in the winter, as the walls don't cool down enough for vapor to condense. Single pane windows also gather a lot of condensation.

I'd assume mould was a bigger problem in warmer months in Japan though - it's often very humid. Winters are relatively dry.

You can build housing that doesn't get mouldy and is well insulated by having proper insulation and a modern ERV. It seems like Japan's policy of 'disposable housing' doesn't stand up to expensive electricity.

> You can build housing that doesn't get mouldy and is well insulated by having proper insulation and a modern ERV.

During the rainy season, humidity in (mainland and southern) japan gets above 95%, for 6-7 weeks.

And then of course, there's the local building habits, like the cardboard houses of the US.

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