Hi again, draft of cold air sinks down wall, warms & releases moisture - or is it warm air cools, reaches dew point & again...bingo...wet. Maybe insulate with some bubble wrap. I have thought of this when parked in the sun. Do you have thermal pane or regular glass & are seals still ok?
Try a pad on the mattress or see if Phoenix still sells a temperpedic made to size. Call or email Amanda & ask. I put a topper pad on mine & it is much better. Oh, is it right side up?
kevin