Is it a red or white bulb. Reds you can leave on as long as it doesn't fry your snake, whites only during the day because the bright light will stress your snake. UTHs are the way to go. Also you can insulate the 2 sides, back and half the front with blankets taped to the tank AWAY from the light. Don't put cloth over or around the light. You can use foil on 2/3rds of the top to help keep heat and humidity in some. If you can stand it try to keep the temps up in your apartment till you can get an appropriate heat source, or move the snake to the warmest room. You can adjust the vents also in your apartment so that one room is warmer.