- Q.I am remodeling a 1920s
house that has the original knob-and-tube wiring. I
would like to blow cellulose into the stud cavities but
am guessing that it's not safe to do that with the
exposed wiring in the cavities. What does code
say?
A.Rex Cauldwell
responds: You're right; it isn't safe. The
reason is that knob-and-tube wiring is designed for
open-air heat dissipation. That means there cannot
be insulation around the wires, which would be the
case if you blew cellulose into the wall
cavities.
The same applies for knob-and-tube wiring in the
attic or between floor joists. You shouldn't have
any insulation around the wiring — not
even fiberglass.
Rex Cauldwell is a master electrician in
Rocky Mount, Va., and author of Wiring a
House.