I live in Northern Canada and have learned the hard way what damage zero percent humidity brings to ANY AND EVERY stringed instrument.
First hard lesson;
Humidifying a room does not adequately humidify the guitars in it. It may be sufficient for solid bodies but for acoustics/semi acoustics it won't work unless you humidify up a point where mushrooms are growing out of your walls.
Second hard lesson:
The only way I've found that works is to use an oasis type humidifier that works with a gel and NOT a sponge. What a sponge gives, it also takes away a when it's dry.
Third hard lesson;
The guitar must be stored in its case with an oasis O-H5 (the big one) humidifier. Even when adequately humidified, the guitar will still exhaust the humidifier every 5-7 days.
That's ok..you can't over humidify a guitar as long as you do it gradually as in the above mentioned strategy..do not use 2-4 humidifiers.
Fourth hard lesson
Case humidifiers don't work.
Humidifyinge headstock or dropping a humidifier in the case is useless. When you close the case, the soundhole is blocked by the case. Humidity can't get in. The result of a drying guitar that has its top under pressure and braced, is that the sound board in front of the bridge will drop and the bridge will tilt forward and down causing the notes to buzz as you ascend the neck. This will happen either shortly before or after the top sheet develops horizontal cracks.
There is zero benefit to humidifying the headstock..unless rusty strings are your jam.
Last hard lesson (so far)
Nobody makes humidifiers for semi acoustic guitars..or at least not ones that actually work.
What's needed is one that fits into the f hole in the top of the lower bout. (The f hole on the other side of the electronics). you'll have to make your own until somebody figures it out.
I would close by saying that a properly humidified guitar will resist drying out to the point out damage for a very long time..months perhaps.
So room humidification may act to slow the rate of drying enough that after a couple months, ambient temperatures rise high enough to carry sufficient water, depending on where you live..where I live, no..not a chance LOL
