First, if you are keeping him in a glass tank (or even if you're using a professionally-produced plastic enclosure) you can insulate it using a variety of inexpensive
materials (foam board, cork tiles or on a roll, poster board with foam core, corrugated cardboard, peel & stick carpet tiles, & so on!) That will help you keep the
heat IN the cage where the snake needs it. You'd want to cover (tape securely to) the back, sides, maybe the bottom few inches in front (-leaving a big "picture
window") and underneath the bottom (leave some breathing room if using UTH for safety so it doesn't over-heat- we can explain further if you need more info).