The air outside is extremely dry (<5% relative humidity once heated to indoor temperatures), and the air is quickly replaced by the ventilation. I have anecdotely heard that in the US they have much lower requirements of rate of air replacement than here in Sweden though, so maybe that could work there, but then you would also have stale air, which doesn't sound great.
And if you have your own well, you generally do a cheaper filter targeted at whatever impurity you have (such as an iron filter), rather than a reverse osmosis filter.
With reverse osmosis the water also gets too pure for drinking and you need to add back minerals to it for safety, it is not healthy to drink ultra pure water for any prolonged period of time.
Ultrasonic humidifiers (and others) that spritz water droplets out? They need fed expensive water, or they spread particulates everywhere. Health aspects aside, it's nice living in a house that isn't bathed in something that looks like chalk dust.
Evaporative methods? They're similar in their lust for pure water, and the particles tend to concentrate at the humidifier instead of everywhere else. That accumulation needs to be cleaned up periodically (or parts replaced, depending on how rent-seeking the design is).
Distilled water from the store? That's gloriously clean water, but it represents a money pit that can never be filled up.
RO water? Sounds nice (is nice), but they're expensive and inefficient (producing 1 liter of RO water wastes in the realm of 3 or 4 liters down the drain). The systems need installed, and not everyone has the capacity to wrangle their own plumbing projects.
And as an added bonus: Drinking RO water saps our precious bodily fluids of the minerals and electrolytes that people crave to stay alive, so we also seek to deliberately impurify it.
I guess that means that an ideal path to RO-oriented humidification, we end up with 3 taps at the kitchen sink, then? One that provides demineralized for the humidifier, another that provides remineralized water for drinking, and one for everything else?
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It's all ugly in some way.
Isn't there some kind of evaporative humidification method that is easy and inexpensive to clean? Something I can just feed cheap tap water into, and that I only have to deal with cleaning once a month or something? That sounds like the path of least pain for me in my neck of the woods.
There are a few brands out there but the Philips ones seemed better than the others and the prices were not as insane. I just disliked their marketing and buzzword filled content but otherwise they seem OK. Oh and you should know a lot of their stuff now are internet connected(disabling it will make you lose some functions but otherwise the device still works) and have touch buttons and screens etc. It's unfortunate but this seems to be where every device is heading.
I do agree with you that this seems overly complex. You can pretty much do it yourself if you'd like to take on a project. A fan and a constantly wet rag has the same function but is not as compact.
I prefer dumb, but I don't mind if it's smart. Especially if I can integrate the smarts into my Home Assistant rig.
I built a humidifier once. I just used the Instant Pot that was already on the countertop. I filled it with water, set it to "Keep warm", and it slowly evaporated the water and left minerals behind.
This worked fine (it was safe, if inefficient).
But monitoring the consumption of water and the improvement in humidity showed that to actually raise the humidity to a comfortable point would and do so throughout the house would use a lot of water.
And I want to do more with my time than fill humidifiers back up. :)
Also, y'know, your lungs. Deep inside your lungs.
Running tap water in an ultrasonic humidifer's going to spike the particulate pollution (PM1/2.5/10) throughout your entire house by hundreds of ug/m^3. And it seems that children are particularly prone to inhaling this stuff and having it deposited in their lungs (~2x more particles and ~3.5x more mass).
They really shouldn't be used with anything except distilled water. The things should come with a continuity tester that disables them if the water's conductive or something.