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Comment by dragonsky67 | Hacker News Reader

I'm in Australia, and I've lived in a lot of areas both inland (hot dry) and coastal and humidifiers are that common here.

What is it in the US that creates the need/demand for Humidifiers?

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Cold outdoor temperatures cause indoor humidity to get extremely low, because cold air can't hold humidity well.

Today where I live, the relative humidity outside is around 50%, and temperature -5c. That puts the absolute humidity around 1.7 grams per cubic metre. At 20c indoor temperature, that equates to around 10% relative humidity. Far too low.

Thanks for the info... It's rare to see regular temperatures here much below 10 deg C and even then, most people live on the coastal plain so humidity rarely gets very low. Good to learn the conditions others have to deal with.

Cold air has less of an ability to hold moisture, the colder the air the less moisture it can physically hold. So 100% relative humidity at 20°F is much less moisture than 100% relative humidity at 80°F

When you heat cold winter air to a comfortable room temperature you are increasing it's ability to hold moisture without adding any moisture. This has the effect of decreasing the relative humidity. The bigger the change in temperature the more you decrease humidity by heating it.

Winters are cold enough in some places that indoor relative humidity can easily get so low it effects humans negatively - dry cracked skin, dry cracked mucous membranes, sore throat, static buildup. Add to that low humidity aids in the spreading of viruses.

Winter temperatures in the US midwest and northeast with average daily temps far below zero (C), combined with leaky old houses. The stack effect draws in cold, extremely dry air at a rapid rate.

Without a humidifier, you can actually feel the dry air and it gets pretty uncomfortable at night. The skin looks dry and flaky in the morning. If you happen to catch a cold, your symptoms get worse because your mucus tends to dry out (the only remedy is to then go and stand in a high humidity bathroom for some-time or inhale vapors. You need it for at-least 2-3 peak winter months in the eastern part of the US.

Winter.

Winter in a house with a forced-air heating system just makes everything far worse. If you have the opportunity and the means, you want to go with a boiler, radiant in-floor heat, etc. Anything but forced-air.

By the way, in the winter we almost never use the dryer when washing clothes - always hang them up and they dry quickly and add their moisture to the air. We also open the dishwasher door as soon as it finishes and let the moisture evaporate into the air. Etc.

The problem with low humidity in winter isn't forced air heating, it's air leakage. But since most houses have poor thermal envelopes, your statement turns out to be mostly true.

It is heating. Forced air doesn't make any difference. Forced air is the most energy efficient (electric is slightly better, but much more expensive), so in cold places you get forced air and also the need for humdification

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