That may actually be in centimeters, not inches. If that's the case, it's 4'x2'x15" which is pretty nice for an adult female.
I do agree on the heating issues however. You're either going to need the ambient temperature in the room to be close to the coolest you'll need inside the enclosure, or you'll need some other way of doing it.
Heat cable will still need to be controlled and do be careful on how it is set up. It's rare, but accidents do happen where snakes will get tangled or try to eat a warm cable if it is inside the habitat and loose. Make sure you are using something like cured foam or silicone to hold it down, not tape.
Any form of heat will need to be controlled to where the snake cannot access it where temps will be over 92 degrees.
This means properly boxing in CHEs and lightbulbs. and that will decrease some space in the cage as well, since you don't want the caging to be overheated to injure as well.
Graphic images.... but this is a snake rescue I took in. The culprit was most likely a heat bulb he wrapped around inside his breeder's habitat or the heat pack shifted while he was shipped and he had no was to escape in his deli cup.
https://imgur.com/a/yGR69ib