This morning I was standing in the hall just outside the shop door (room over garage) talking to my wife. I happened to lean on the wall long enough to notice it was really warm. On the other side of it is my daughter's closet, so I popped her door open long enough to confirm no fire or smoke or anything.
Thinking it through, and poking around in the garage, I have verified that the
vent stack for the gas furnace and water heater goes through there. When she wakes up later I'll check to see if the closet wall is also warm. It's 27 here so the furnace is going pretty steadily, but it seems to me that the inside of the wall should not be warm, with triple wall duct, unless there's a leak.
Anyone have any thoughts on this before I cut into the wall tomorrow?