Greetings!
In a former step van I had with a daylight roof, if the vents were closed it was an oven inside.
It had a vent on each side, down low, just ahead of each sliding door on the front of the van. On the sides at the back of the van, on each side just below the roof line, it had another vent on each side. All of these vents were louvered to keep moisture out.
With all of these vents open, even in extremely hot weather, they would maintain the interior temperature to match the outside temperature with no fans involved. I think this might be called convective cooling. Whatever it is called, it did make a HUGE difference.
Sometimes older, and/or simpler technologies can be more effective, or just as effective as newer and more complicated technologies. If two or more techniques obtain the same results, the simplest is always the best solution.
Cheers!
The CamperVan_Man
