How do you keep the enclosure at a safe temp?

[Bogertophis]

...It is UTH's that do not increase ambient temperatures by more than maybe a degree or two, if at all.

And sorry, but that's not true either, lol. Like the other heat devices, you might not overcome really cold temperatures (depending on the brand & type of UTH you use)
but I've been using it for decades, & all heat rises. UTH is actually the most efficient since the heat goes right up into the cage, & IF you bother to insulate the cage and
also under the UTH also (leaving the required gaps for the UTH to "breath" & not over-heat) you will maximize the efficiency of the UTH. You also need to size it correctly
for the needs of the kind of reptile being kept and the size of the cage. Many reptiles do best with a basking spot, so extra overhead heat is often needed for that. Also,
some brands/types of UTH get HOTTER than other types...so do your homework for best results. I'm a fan of Flexwatt because I keep mostly colubrids & don't need as
much heat in my cages (glass tanks!) and it's low-wattage & very dependable, but it doesn't get as hot as some other types. (It's also made of thinner material.)

Where I would NOT advise using UTH is when you have an enclosure that's say made of wood...wood is a great insulator so the heat will have trouble getting
thru to the interior of the cage, and you'll be running it so much higher that it's apt to over-heat & burn out...could even be unsafe. Plastic cages are not as
good at "insulating" and the UTH heat WILL rise into the cage, but for the amount of heat needed for something like a ball python, or to overcome a cold room,
you'll likely be warping the plastic from the UTH...so carefully consider both the kind of reptile and the kind of enclosure when choosing how to keep it warm.