There are several factors in how well the a/c works. My van has very good insulation, and fewer windows than most. The windows it does have are not glass. They are double layer plexiglas with about an inch of space between layers, making them pretty good at insulating. They also have built in reflective shades adding 1 more layer of insulation. We camped near the Grand Canyon in 114 degrees and were completely comfortable. While a full wrap around glass windows give the open, airy appearance, they are terrible at separating outside temperatures from inside. Even reflective window film only blocks ultraviolet heat, not radiant heat that comes through the glass.
Next time you are driving on a hot day, feel the inside of a window that is out of the sun, it will be the same as the outside temperate, the more surface area of glass that you have, the more a/c you will need to overcome it.
