I have a split level home (1950's) i had central air conditioning installed, with the air return in the headspace over the stairs to the upper level.
The attic space has been insulated with a thermal blanket silver insulation.
Some of the ductwork was run through the closets in the bedroom from the attic.
Now I have a wicked cold draft on the stairs, flowing down to the living room level. I have cut and plugged the filter space on the air return with a 3" slab of polystyrene insulation. But it either does not work, or I am missing where the draft is coming from.
Can you please help?