we have our night box finished outdoors, but i'm struggling with low humidity in there. like 19-20%. i realize it's outdoors and my torts 3 years old, so i'm not concerned about getting high humidity, but that oil heater is really drying it out and the hay in the box is really brittle. it's cold enough she's spending most of the day in there and not going out much. i am soaking her a couple times a week, but wondering if there's something i should do to raise humidity and if so ... what?