Well, since no one else has jumped in...
Our experience with our factory windows is that they suck. I'm not sure what we can do differently. I know that some of them have been resealed already, but there are tons of air leaks. In February, we were traveling in a blizzard across Nebraska. There were snow drifts inside the bus!!
We're really hoping to be able to replace them with better quality RV windows someday. I do however plan to use the bus windows in a horse trailer!
I realize that my comments probably don't help. But I didn't want you to think that no one cared! Best of luck.