Make sure his habitat has a warm end and a cool end. Warm end 95-100F, cool zone as close to 80 as you can get. Your ig can sense the het n his back, and his body will tell him how high a temp he wants to be in. If he needs a lower maximum heat, he will just settle down a little farther from the center of the hot zone. Place the heating and UVB on the far side of he hab. Normally the natural un-enhanced warmth at the cool end is at least 85F at all times, if the hab is not made with mesh.
If it is a mesh hab, you need to set up a thermostat at each heat zone to keep their temperatures at the right level.
This hot-cool thing is a must-have for healthy iguanas, for reasons I can't explain here.
Mesh saves money in construction, but it requires more technology to make it habitable by iguanas, which are extremely climate-sensitive.
Have you thought about putting one or two cool-mist humidifiers in the cage?