It's about my 40-yr old 2-storey house in midwest Canada. After taking off part of basement ceiling, I found something weird with a heating duct. It runs up from basement to main floor along an exterior wall (built into the fiberglass insulation), and maybe further up to the second floor, and to attic??? I'm sure no heating vent in the house uses this duct. I just can't figure out where is goes. It sends hot air to attic to do heating? possible for an old house?
please help solve the mystery. Thanks.