The basking light shouldn't heat the entire enclosure and most likely if large enough (enclosure) it won't be able to. Chams need different temps within their habitat so they will be able to regulate their bid temp. The temp gradient should be about 10 degrees from top to bottom. I go between a 60w and 75w bulb depending on time of year. Also a regular incandescent bulb will work just fine compared to a pet store bulb. It doesn't need to be blue. Much cheaper to by household bulbs too.