Knob & Tube w/ Cellulose

[rlowe82@gmail.com]

Hi--

I am in a house that was built in 1921. It has knob and tube and is still running electricity that way. We've had an experienced electrician come and inspect all the wires and breaker box and retrofit all the plugs to be grounded. We asked him if cellulose could be blown in over the knob and tube in the attic and he said that'd be fine because the wires are still in good shape.

I called an insulation company with experience in knob and tube and they said it's fine, as well. Especially because cellulose is non-flammeable.

I still have reservations, though. Despite both the electrician and insulation company saying it's safe, I'm worried.

Should I be? Has anyone else blown in cellulose over knob and tube?

We are planning on only blowing in the cellulose in the attic, not the walls.

Thank you!

[HayZee518]

I'm a master electrician of 42 years experience and all my inspectors say NO to blown in insulation over knob and tube. The wiring was installed on porcelain knobs approx 2 1/2 from the joist surface. Why you ask? Because of radial cooling. Knob and tube wiring, a jute fiber weave over rubber insulation over a tinned or not tinned metal wire needs free circulating air to be effective over its entire length. branch circuits used this type of wire in a woven tube called loom perhaps over its length, perhaps not. it was free fed into cast iron "boxes" if you could call them boxes. much of it was just poked through holes in the plaster and lath to fixtures. splices were wrapped, tinned and soldered then taped. a poor splice meant heat and eventual failure and a possible fire. NO, NO BLOWN IN INSULATION FOR ANY REASON!

[rlowe82@gmail.com]

Thanks, HayZee.

So what kind of insulation do you recommend for knob & tube?

[HayZee518]

NOTHING REALLY. replace the knob n tube with romex or bx and you can blow in whatever you want!

[Stayouttadabunker]

I agree, I lived in a very old house once and had to have all the wiring replaced!
It was a very expensive project to do.

The United States National Electric Code (NEC) section 324-4, forbids the use of loose, blown-in, or expanding foam insulation over Knob and Tube wiring.

You only options are to leave it as it is or
replace all the K&T wiring in that home.

[rlowe82@gmail.com]

Hi everyone,

This thread has been really helpful.

I spoke to an electrician who said he could replace the knob & tube that is in the attic to Romex so that it would be safe to have cellulose insulation around it. His process would be to take the knob & tube that runs up and inside the walls and add a junction box, where he would then change out the existing wiring and add the Romex. The Romex would run throughout the attic, which he said is far safer to cover in cellulose.

Any thoughts? Does this seem like a solution? He said that it would be a huge job to replace ALL of the knob & tube, including the wiring that runs in the walls and through the lathe & plaster, so this would be a good way to ensure safety while still having insulation.

Please let me know!!! Thank you much in advanced.

[HayZee518]

I rewired a house in massachusetts that had knob and tube on the second floor. It ran [him] about $1200.00 for the rewire. three rooms, lights, switches and four outlets per room. each leg of the knob n tube goes into seperate knockouts of a standard 4 inch square junction box in romex connectors with pieces of loom as protection. one romex cable in one knockout of the box and wirenut splices.

[rlowe82@gmail.com]

HayZee--

Thanks for the info.

Can we modify the k&t so that it is still in the walls, and connects to romex inside a junction box that would be in the attic? That way the attic can be filled with insulation. (the wall would not be.)

I imagine it would be something like this:

wall outlet --> k&t in walls --> junction boxes --> romex in attic --> circuit breaker

[HayZee518]

every place you have a drop for outlets and switches, put a junction box and plate. remember these boxes need to be accessible or you'll be creating another code violation.