check where you vents are positioned, especially center vents if they are set on "cold" (up is cold, blue box vs. red box). if you have a bunch of cold air at high blast aimed towards the windshield, you willl get condenseation and in the summer build on the exterior glass. place the vents to point inside the cabin. sync the temps to the same temp IMO, and use recirculate. blue ='s cold.
i live in a very fluctuative climate with dewpoints and humidity, and i haven't had a problem. good luck!
Auf Wiedersehen 12 550xi