I think I'm going to run the fans upstairs in the windows, and leave the AC off. Our temps aren't getting really cool at night when the days are warm. But the fans help. Last night though it was in the low low fifties overnight and today will be in the high 80s. Gotta love Ohio weather LOLWe haven’t run AC yet either. It has been cool at night. I would not leave your windows open on the main floor. Heat rises so maybe open an upper floor window? Or set the AC to go on when then temp reaches 80 in the house. This is assuming you have central.