Tubs are best at keeping in humidity and heat.
I use a 20 gallon long glass cage with screen top, and what I do is I cover 3/4 of the screen with aluminum foil (plastic wrap might work even better), and have a generous portion of sphagnum moss (also known as frog moss, comes in brick form from petco and such) that I spray daily. I also have a nice sized waterbowl.