I’ve been using a steam humidifier made by Air-O-Swiss. The pads completely eliminate the white dust portable humidifiers have, but you have to clean the machine once a week, fill it up each day, and change the pads when you clean the machine. It’s easy, but it’s still a PITA.
In winter, you need to run it fairly low (35% or less) or you can get too much condensation, which can cause mold on outside walls and window treatments if you’re not careful (this is true of cold water humidifiers as well).
Unfortunately, the whole house system I have is just there to be mythical and make me think it might work. Truth is, in winter in the Midwest, even a whole house system basically sucks.
Similar to Alphasports, I stick a D’Addario guitar humidification pack in each case (they come in sets of three, so one set works for three electric guitars), and use the set of three in the case with my acoustic. They work, they give off moisture when it’s too dry, and absorb it when it’s too wet. The humidipaks are designed to keep the RH in the case at 45%, which is precisely what PRS keeps its RH at in their factory. Incidentally, these appear to be made or licensed by Boveda.
In some PRS cases, the packs can be kept near the neck in the open space, but some cases are form-fit by the neck, so I keep a pack in the headstock area.
They come with cloth bags, they never drip, leak, or smell, and after 3 years of using them I’ve never had a whiff of a problem. PRS recommends them for their acoustics, but I use one in each electric guitar case as well. Because they also work to keep the humidity at the correct level when the humidity is high in summer, I use them year-round. The packs need to be changed every few months in winter, and maybe once or twice the rest of the year.
I think these packs work well enough that I may forego the steam humidifier this year.
http://daddario.com/pwProductDetail...stem&sid=251ca6a2-c6da-4e01-949f-1cfe8b6d0a5f