It's amazing how I have walked down this aisle and never noticed this excellent auto open/close vent. It's made for a foundation, but could be adapted for any number of uses. I just might have to cut a hole in my wall and put this in, just because it's under $17.00! Anyway, I hope this helps.
It has a screen, screws for mounting in a rough-cut hole, and a nice plastic face cap for a clean look and easy insulation. It opens at 70 and closes at 40, which I don't love, but it might be perfect for someone else looking to just keep from overheating.