Our greenhouse has two windows as part of the roof that operate automatically to open at a certain temp. They are not electric. I am not sure how they work--on some expansion principle, I suspect. (This was a kit greenhouse.)
We start seeds in it in the spring and then in the summer we grow cukes there cause the beetles destroy them if we grow them outdoors. The door has a screen but if it is really hot, we leave the door propped open all day.