I have one ceiling vent that develops condensation to the point of dripping on the floor in my bathroom. I made sure the vent is sealed around the sheetrock, no obstruction to the air intake, clean filter. When I take the vent cover off it does not feel like there is any moisture in the inside (duct). Any thoughts on how to rectify this? I have no problems calling a HVAC company but it sure seems like I am missing something on an easy fix.