I have a version of this on my bearded dragon enclosure. In my case I used an AC version that can be 'dimmed' but basically the same principal. My pvc enclosures I found air flow to be dramatically increased by adding a vent low and froward. My enclosures are vented high and to the back I added low vents on the front corners. I found the cross venting generates a thermal breeze. It is enough that you can fly a thread on the low vents.