Insulation is a great start. I also have used fluorescent lights to add ambient temps that is quite efficient.

Side turned tanks also will hold heat better as they do not open on the top.

http://ball-pythons.net/forums/showt...arium-Solution

I have a side turned and regular tanks the both run fine in my place until I hit the low / mid 60s then the hot side heaters are under powered and the temp drops. I don't really have too many humidity problems with either tank set up deep coco coir on the upright (cool side only) once moisten it releases humidity slowly and will hold for 7-10 days even in NS with the heating on. (average 32% interior humidity in winter) and nothing restricting air flow on it (screen lid nothing more)