All the vinyl windows in a house I purchased a few years ago are leaking air between the upper sash and the jamb in the middle of the window (where the upper and lower sashes meet). I have no idea who manufactured the windows.

Thanks to this forum, I found a post that pointed to an adjustment screw in the sash that corrects the bow in the jamb. I stripped the screws in 3 windows trying to adjust the bow (its that bad) with only minimal improvement.

The gap between the upper sash and the jam is significant -- I have to put a strip of tape on window/jamb joint to stop the cold air.

Is this a job that a window repair man could handle, or will I just get a sales pitch for new windows. Thanks.