Never keep guitars at 0% humidity. They really should be kept in a room with 50-55% humidity. To little or to much moisture will warp the wood of the guitar and possibly cause irreversible damage. They have in case humidity controllers that work fairly well. You can get them from most guitar stores.
I have a fender telecaster and a taylor acoustic guitar i just purchased. A couple of months ago, I just finished my basement and decided to put my guitars down here. My fender and my taylor acoustic are kept in cases but I heard that it needs to be kept in places with no humidity. My basement is probably 15 degrees cooler than the rest of my house. So my question is, would this have any effect on my guitars that are kept in cases?