I know with, or without the windows open on my current Snugtop, the inside gets damn hot in the summer. The Smart Cap has something, I forgot what it is called, that pushes air into the cap when the vehicle is in motion. The two side windows on the Smart Cap I actually saw open up completely, but you can only open both side windows completely when parked. Otherwise the two side windows have two small sliders. Heat is a huge issue for me because I train Combat Dogs. However, heat is only an issue for me when I am parked and busy training other dogs, which is when my dog is inside the shell, otherwise my dog sits behind me in the cab.