I have a house built in 1900. I believe it's a balloon framed house but there are no open stud bays in the basement as the wall is built on the floor plate. Once I'm through the floor plate I can go right to the second story unimpeded (and I suspect all the way to the attic but from what I can tell there is a top plate up there also).
The interior is lath and plaster and the exterior is diagonal plank sheathing under the original wood plank siding, at some point in the past 30 years this was covered with vinyl siding and it looks like a thin layer of rigid foam insulation (1/4").
The general consensus seems to be that it's unwise to fill the cavity in these exterior walls, but do the walls need a stack effect airflow to properly vent also? Can they be sealed top and bottom to prevent that or will this also cause moisture issues? I'm considering tackling air infiltration by sealing the rim joists and the top plate of all the walls in the attic.
From what I can tell the attic has soffit vents but I can't see a ridge vent. The attic is finished but I have easy access behind the knee walls on one side, there is a hole where some electrical wires and pipes come out and there is a significant airflow coming up into the attic (that's not an exterior wall though).
To add complexity I have pocket doors that essentially open the wall cavity into my living area (the pocket doors are on interior walls but one side abuts an exterior wall), I also get a fairly significant breeze out around these doors when it's cold, so there is significant air infiltration coming from somewhere.