Hi, Francois.
I don't think you need to worry. I keep all my T's on a set of shelves with a large heater in front if it in the room. My T's have all been glued to the front sides of their enclosures since winter started. My guess is that they stay in the part of the enclosure that's the warmest (unless it's too warm, then they will move).
As long as your T has a cooler place he can move to and the enclosure stays humid (either by misting or a water bowl), then your T should be fine.