what is your rack made of? I would try insulating the sides and back with some type of foam insulation. At night my room gets down to 67 but the ambient temp in my tub stays at 81-82 degrees. I use belly heat for hot side and side heat around the whole tub to increase ambient temps. Its defiantly easier just to heat the room to 80. however, my snake room is where I sleep so heating the room to 80 would make it hard to sleep.