In a room that may have had some kind of condensation on the past, how should one go about sealing the area around the vent hole in the ceiling, specifically to reduce the likelihood of returning condensation on the future?
This room is on the second of two floors in a residential building. The second floor HVAC system runs through insulated rigid ducting in the attic space.
The room in question seems to have had condensation issues in the past (dark spots were on the windows, and see attached image of ceiling vent to be replaced).
It looks like someone previously tried to seal around the edges of the drywall of a ceiling vent (see ceiling image attached).
According to the owners, it was unoccupied for likely several months, but less than a year at one point several years ago. During the time the building was unoccupied, it's not known if the HVAC was functional or not, but the concern is high temperature fluctuation.
This building is in Southeastern North America, in an area that is regularly humid.
The vents in this room are already being replaced.
How should one go about sealing the area around the vent hole in the ceiling, specifically to reduce the likelihood of returning condensation on the future?
**Edit to fix unuploaded images.