I have a 1948 home. 1900sq feet - 950 up and down with a finished basement...walk out in the back. We have a new gas furnace.
The previous owner moved the master bedroom downstairs - put in a big closet and french doors out to the garden. The furnace duct is situated on the ceiling, close to the outer wall and adjacent to the french doors. The inside bedroom wall that is perpendicular to the outside wall has a square cutout (approx 12"X8") at the bottom of the wall (at the far end of the wall, away from the outside wall). The cut-out has a grill in front of it, but is not connected to any ducting. There is a similar cut out in a parallel inside wall of a small room/closet that was used as a storage area by the previous owner.
The problem is, that these holes in the wall often seem to let in a bit of a stale, stuffy smell, so I'd like to seal them up, but I don't know if they have a purpose. I've been reading a bit about cold air returns, but given that these don't seem to be connect to anything...? But I want to ensure proper ventilation, but don't think the stale air would be helping that.
Thanks for your help.