I have a 54"x20"x20" glass enclosure for my ball python and it really is hard to keep the heat in there. I covered most of it with blankets and will probably put plastic around it this winter. I can't fully heat everything but I can get the important places. I have 2 medium heat pads under his hide on the warm side (1 large would probably work the same but my local store only had mediums) set on a thermostat to 90 degrees, I check with a temp gun often to make sure it's working and at the right temperature. I have a small heat pad with a different thermostat set to 80 degrees under his hide on the cool side. I also have a 100 watt CHE and a 100 watt black nightlight (my ball python is so active with the moonlight) over on the warm side. Of course it doesn't reach very far but at least my little guy has a basking spot if he wants to use it at night (he does). I keep my house warm in the winter, usually at around 76. My ball python is perfectly happy with this setup, he may not eat in the winter but this is normal for ball pythons but he sure does like to come out and play in his room showing that he is a happy snake.
Edit: Forgot to mention he has bamboo perches up high so he can go bask under his CHE and black light and be comfortable.