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rlowe82 10-28-2011 02:45 PM

Knob & Tube -- Cellulose Insulation?

I posted this in the Insulation subject, but realized it may be more suited here. Moderator: please delete my previous post.

I am in Los Angeles in a house that was built in 1921. It has knob and tube and is still running electricity that way. We've had a licensed 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. A lot of forums say to replace the knob and tube completely.

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!

nealtw 10-28-2011 04:51 PM

Might be a question for your insurance company.

speedy petey 10-28-2011 09:28 PM


Originally Posted by nealtw (Post 62677)
Might be a question for your insurance company.

What would an insurance company know about electrical and building codes? :confused:

JoeD 10-29-2011 07:43 AM

Unless you have some different type of K&T than everyone else it is a free air system and is not supposed to be buried in insulation.

How did the electrician retorfit the receptacles to be grounded without replacing the K&T?

joecaption 10-29-2011 08:06 AM

That was my first question also, if he just changed the outlets that's against code, the outlets will still not be grounded. The only exceptable way to do it is to change to a GFI outlet. It still would not be grounded but would prevent someone from getting killed.
Old knob and tube can not be spliced or worked on to replace just some of it, it would all have to come out at the same time.
If you for some reason had all the walls exposed replacing the wiring would be a no brainer to have done.
If you do rewire then I'd also bet the incoming wire from the pole should be changed and a new breaker panel installed.
It would be expencive to do but a huge safety feature and increase the resale price of the home.

JTGP 10-29-2011 06:07 PM

I would like to see what the Electrician did....

Can you provide a picture of a outlet he made with a ground.


nealtw 10-31-2011 10:45 PM

Speedy: Some insurance companys will not cover a house with K&T covered.

JoeD 11-01-2011 06:27 AM

Some insurance companies will not cover a house with K&T, covered or not.

rlowe82 11-03-2011 10:53 AM

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.

joecaption 11-04-2011 07:31 AM

I think you will find it's illegal to do that. I'm sure one of the electritions on these boards will back me up on that. Several reasons are the fact the insulation on the old wires will be crumbling by now so there's no 100% sure way to make a safe connection, old wiring will have no ground but the new wires would so I'm sure someones going to connect up a grounded outlet and have no real ground. That old wire is most likly under sized.
I big job to replace the wiring, yes but well worth it. It will increace the value of the home, give you the chance to add more outlets, make the home a lot safer, no more over loaded circuts.
You would be shocked to see what's behind those walls as far as the wiring goes. Splices with no juntion boxs and just old rotted tape around the wires, burned wiring, places where critters have eaten through the insulation.

I see it evertime I open up a wall in every old house I've worked on.
One I found had caught on fire and had burned up the whole stud bay but for some reason did not burn down the house.
All he has to do is add outlets in the baseboards, not up into the walls.
I'd also guess those walls have no or little insulation inside them.

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