I have had crap luck with moss. It needs to stay moist 24/7 which means either a misting system or constant contact with water. My moss has died off even in my GTP tank with 70-90% humidity.

If you're trying to increase humidity I think you'd be better off taking more drastic measures. E.g., add a humid hide, cover a portion of the top of the cage, spray more often, change heat sources, etc.