I apologize for the late contribution, but I have bee busy trying to find the best way to humidify 4 (four) guitars, get a replacement guitar to star my lessons (new member) and get a decent price to fix the lifting bridge on my Cordoba C7, resulting from too low a humidity level this winter.
Purchased both Humidipaks and Oases, and did not get the in-case humidity increase (levels) needed. Purchased a room humidifier, and it has done the trick. It even help a bit with the sharp fret poking out the board on the C7, although it did not correct it completely--guitar now at shop, being repaired.
To me, it makes sense to purchase a room humidifier that shuts down when the relative humidity reaches a level you pre-set, let's say 55%; that saves power, extends how long the unit works without reliving, and avoids over-humidifying. This may also allow you to make the area as weather-tight as you like, and keep condensation, etc., to a minimum, if the weather becomes more agreeable. Obviously, for those who do not have a whole-house humidification system, stand-alone room humidifiers are like pets, that, ideally, should be fed and cared-for all the time, even on those occasions when we must see Mom, etc., or pay the consequences, on both sides.
In spite of the less than sterling results, I am keeping the Humidipaks, because they promise to keep humidity at 55% max, and one of my guitars suffered from over-hydration the first year I got her. The Oases are not as versatile, but they show you when they need to be refilled, and are less expensive to maintain, since they only require more water--non-distilled in my case, since my tap water is pretty soft.
The lessons on the effects of humidity on the health of guitars has been an expensive one for me, making it unforgettable:
1. All solid wood guitars do not react the same way to the same levels of humidity. One out of four guitars began to disintegrate at RH averaging 30%.
2. Pay attention to changes in your instrument, no matter how subtle. My C7 began to show shoe fret points before I noticed anything else.
3. Drastic changes can be taking place without you noticing. Although the bridge had begun to lift under the strings, the guitar could be tuned to perfect pitch, and it would sound as if nothing was happening.
Hope some of all of this rambling helps.