Most of them are heated basking/heat lights. Some of them have belly heat or a strip of heat tape down the back, all heat tape is concealed. I haven't heard back from anybody having issues with their snakes burning themselves on the bulbs. You could also put in a "false" ceiling and use glass to keep animals away from the heat source.
Thanks for the comments!
Kronos, unfortunately I didn't take any progression pics. However, if you are feeling up to building a viv for your boa, I could walk you through the steps. PM me if you're interested