LLigetfa said:Hotter air is lighter and so more buoyant and as a result will want to rise. As it rises, the cold heavy air will rush in to take its place.
The reason I suggested the closed door test was that would reduce convection as a source or the draft. If air infiltrates under the door, that suggests outside air may be flowing through that room and seeking a route under the door.
I have a two storey house with the wood stove on the main floor which is open concept. The heat naturally rises up the stairwell and conversely, the cold air from upstairs rolls down the stairs. It is quite noticeable and does not indicate that I have outside air infiltrating from upstairs. The upper floor after all, is above the neutral pressure plane so air would exit, not infiltrate through any opening in the building envelope.
Thats exactly my concern here!