Your Habitat must have a basking spot that has a temp. of 85 degrees of more. 95 degrees is a good temp. You do not want it to be above 100 degrees any wherein your habitat because you iguana could over heat. The oppisite end or bottom of your habitat should be 70-75 degrees, that way your iguana can thermoregulate. He can move closer to the heat source to raise his body temp or farther away to lower it. This is important because iguanas body temps. must be 85 degrees to digest food.
The heat source should be a heat bulb of some sort I recomend the new full spectrum mercury bulbs made by Zoo-Med and ESU reptiles. If you can't afford one of those get a heat bulb/ flourescent bulb combo that will provide the UV rays your iguana needs to survive. The only flourescent tubes I use are the Zoo-med reptisun 5.0 and the Zoo-med Iguana light 5.0, because of their high UVB outputs.Iguanas need UVB rays to form Vitamin D3 and calcium. The best way to get these rays is exposure to un-filterd sunlight (glass windows filter out most UVB). Next best is full spectrum florescent tubes.
You should also have a secondary heat source for night time heat. In a large cage I recomend a ceramic heat emitter wich are now widely available though Zoo-med. For a small cage or glass tank an under tank heat pad works well, but with these you must be careful your Iguana dosn't burn his tummy. Never use a hot rock because they can create hot spots that can burn a reptile!!
Chewie is now over 4' and has a clean bill of health.
