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Comment by throw0101a | Hacker News Reader

> Compound that with the absurd humidity and mold problem endemic to pretty much all of coastal Asia (trying to keep your house mold-free is a losing battle after a certain point and it's unavoidable) and the cost and effort of repairs far outweighs the ease of just tearing it down and rebuilding.

Worse than, say, the US South? Just make sure you have air and vapour tightness, with a good whole-house dehumidifier and you should be set.

Good building (science) channel from builder in Austin, TX, where humidity is a thing:

* https://www.youtube.com/user/MattRisinger/videos

View on HN

> with a good whole-house dehumidifier and you should be set.

Central air conditioning is not a thing in Japan. People install one split duct heat pump per room they expect to inhabit during summer/winter (generally living + bedroom) and only run those when they're in the room and for as few hours as they can (electricity is expensive)

Air conditioning != dehumidifier. One controls air temperature, the other moisture levels.

While air conditioning can reduce humidity, if you have good insulation then your your HVAC won't run that often, but things like cooking and bathing will effect humidity levels, and so a separate apparatus is really needed for that. They're not unreasonably sized:

* https://www.youtube.com/watch?v=OKJnP_6uxcg * https://www.youtube.com/watch?v=D3wd2yVwzvE

My point is just that Japanese homes are not built with any ductwork at all, aside from a vent above the stove and in the shower/bathroom. A "whole-home" device like those you linked would require installing air ducts to every room, and the homes just aren't designed for it.

Actually you wouldn't have to duct the whole house: humidity does not concentrate like heat does, but rather diffuses. So even if you only have a dehumidify one part of the house, the moisture level would level average out (over a given period of time).

Though this does depend slightly on air circulation, but a couple of tubes (e.g.) connecting floors would help balance things out.

Japanese companies produce many quality products that deal with indoor air quality:

* https://news.panasonic.com/global/topics/2017/53539.html

There are stand alone units as well:

* http://www.survivingnjapan.com/2012/08/a-guide-to-dehumidifi...

All that said, a proper building envelope is the first thing that needs to be done. Don't know enough JP codes and construction techniques to comment on that though.

It’s not just the inside that molds, but the outside. Going to an even more humid place like Hong Kong or Taiwan, you’ll see most buildings, bridges, signs, and virtually everything covered in a permanent cake of black mold.

It’s bad around the US south, but it’s really far worse in Asia. Few structures are considered permanent.

Few structures are considered permanent.

Not sure if this is meant as hyperbole, how do you explain Japanese buildings built during the 7th century still standing today?

They are reconstructed.

https://blog.gaijinpot.com/problem-with-wooden-buildings-in-...

IMHO this is failure of layering:

* https://www.buildingscience.com/documents/insights/bsi-001-t...

Moist areas should not be able to come in contact with cold areas: if they do, you have a problem with thermal bridging, which leads to condensation.

I'm wondering if the mould problems are made worse by the fact that there's already a ton of mould there, spreading spores rampantly. Combine that with a density the US South doesn't even come close to reaching, and you'd have to go on whole-area eradication program to get it manageable.

Mold growths under specific conditions which can be controlled:

* https://www.youtube.com/watch?v=CK4xr7faQYA

Tokyo (for example) seems to have more extreme weather than Austin, notably it has twice as much rain on average.

It compares a bit closer to the Carolinas I think. However, Japan has a rainy season as well (usually about mid June to end of July) where it's very humid. It usually dries out a bit in summer (August to mid October) because the temperature goes up.

I remember the first year I was in Japan trying to dry my shirts on the line in the rainy season. All of my clothing was cotton based and quite a lot of it got moldy on the line! Most Japanese clothes these days have at least some synthetics in it so that it dries quicker.

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