I'm in southern Indiana. Here's what insulation did for me: I have windows; so in the winter the sun would heat the inside up nicely, and the insulation allowed that heat to stay inside longer into the night. The inside stayed about 10 degrees warmer than outdoor temps. In the summer, it allowed the overnight cooling to be maintained longer throughout the day. I'm kicking myself that we did not plan for more ventilation openings (because they can always be closed off during winter cold)...but the insulation did help in our case. We use window fans as well.