My house has a short (15') interior wall between two bathrooms. The ends are up against two closets. All the pipes and septic stack are in the wall. The bottom rests on a concrete slab and the top is up against the ceiling. The attic is filled with about 8" of pink bats for insulation.
Recently, I had to open a 8" hole in the closet on one end of the wall just above the floor. There was a fairly strong cool draft coming out of the hole. My guess was that the draft was outside air temperature, but I can't figure how outside air was getting in.
The draft must be coming down from the attic. There are a few places where electric cables go through into the wall. However, I can't believe there is enough space around them to admit the amount of air I was feeling.
Any guesses? Thanks.