JuicemanJim:Welcome to ECN!!!
I have run across similar scenarios, but not to the extents found on your Project.
Most I saw was maybe Three concurrent Studs, with the "Older" NM Cables running through them, having the
"Tar Seepage" issue.
You may be on to something, regarding the Lightning discharge, but the overheated Conductor / Cable Insulation sounds more accurate - especially since the Wall Cavity contained Building Insulation.
If the "Tar" was found in well Insulated Southward facing Exterior Walls, the Ambient Temperature in that Wall Cavity could easily reach or exceed +140°F daily; possibly sustaining that Temperature for as much as 6 Hours each day.
That would certainly let the Tar out of me, if I was stuck in that Wall Cavity all day, every day!
Is the Wiring Knob & Tube, or the "Older" NM Cable?
Also, do all Walls have the same issues (Interior Partitions and Exterior Partitions).
Scott
