PSA: That old schoolhouse in rural Ohio taught me a hard lesson about knob and tube

I was rewiring a 1920s schoolhouse near Dayton back in 2018, and the whole place still had live knob and tube hidden in the attic with new insulation packed right on top. Almost got a real shock when I went to pull a junction box because the insulation had baked the wires brittle. Any of you run into hidden old wiring that looked fine but was actually dangerous?

2 comments

2 Comments

shah.shane22d ago

Knob and tube was actually designed to have some air space around it, so burying it in insulation is basically asking for a fire. The insulation traps heat and the old rubber insulation dries out way faster than people expect. You got lucky finding it before something went up in flames.

lucas6322d ago

Gotta push back a little on this. The whole "air space" thing is true for old systems, but if you use modern cellulose or fiberglass with proper fireproofing and keep the wiring away from loose fill, it's not the death sentence everyone makes it out to be. I've got a 1920s house with knob and tube in the attic that's been insulated with blow-in for 15 years now, and no issues. The real problem is people using the wrong type of insulation, like loose fiberglass that settles right on top of the wires, or not checking if the old rubber is already cracking before covering it up. Plus, a lot of those historic fires happened because of bad splices and overloaded circuits, not just the insulation itself.