it's in a PVC cage, and it's hard for me to help as I'm not sure the exact model they are in. The heat should hold better in the pvc cage then the outside ambient air. I have a small tiny heater running all the time, and a very tiny fan on the other side to help cycle the air. My ambient air in that area is around 75+. Are you able to post the model of the pvc cage?

The ceramic bulb I was thinking of was is like this
http://www.petco.com/shop/searchresu...c+bulb&x=0&y=0

(the two on the top) but the first one on the left might work if you combined a light and a ceramic bulb, as long as the wattage allows it.