Hi, I am trying to get quotes for blown-in foam insulation and I need a Electrician to certify i have no live knob and tube wiring in the house. House is prior to 1900, 4 unit. I live on the first floor and I also have finished basement. I bought the house like that. It appears that basement has all new wiring and so do various parts of the house. Common areas like the spiral staircase might have the oldest wiring, which is that stuff wrapped in asbestos i presume. Where accessible in the basement and attic I saw remnants of knob and tube wiring, but nothing live. I also went along in my apartment and took out wall plugs to see whats in there for wiring. All breaker panels have romax coming out, there are no fuse panels. Everything is Square D boxes with breakers. There are few junction boxes within few feet of the panels with romax coming in and wires that appear to be asbestos wrapped coming out. Some wire pairs are wrapped in metal ribbed tubing. So I certainly have wiring that spans decades if not centuries.
Is any of the wiring shown in pics below hazard when blowing in foam or a sure sign I have live knob and tube wiring?
On a side note besides opening every wall plug and switch and looking around breaker panels, is there any other way to know for sure other than gutting the walls?
Thanks
Petar

 

You MAY have some K&T but I can't tell for certain from your pictures. Check these Google images for clear pictures of K&T wiring.

https://www.google.com/search?q=knob+and+tube+wiring&client=firefox-a&hs=oiD&rls=org.mozilla:en-USfficial&channel=np&source=lnms&tbm=isch&sa=X&ei=3904VNeUBNDSigLv54C4BA&ved=0CAgQ_AUoAQ&biw=1152&bih=711

 

Knob and tube (K&T) is a possibility. The bare K&T may be in the horizontal areas like the attic or floor with insulated wire like shown in some of your photos (especially the first picture and possibly the second) for the drops to an outlet.

I also see a junction box in an enclosed space with no access. That is not permitted under modern codes. Your house was possibly wired before building and electrical codes so technically it may be grandfathered in but it's not something that's good to leave buried. Connection points can be a failure point and if it ever develops a problem you've got a major mystery/bug hunt on your hands. The box could be mounted to a wall or ceiling and covered with a blank face plate so you'll know where it's located and have access to it. The big spectre is that since you've found one there are likely others and where do you draw the line? If this were a fix-it-up TV show they'd likely re-wire the whole house or give it a very thorough inspection at the minimum.

 

Thank you guys, very informative.
So I see how the bare K&T in contact with expanding foam is a recipe for disaster. That would be in horizontal areas. But foam is blown in on the vertical sections of outer walls, so when the insulation guy says we have to make sure you don't have K&T he is not just referring to horizontal runs, he is probably trying to say is any live exposed wires.
I also see how it is likely that those old wires in vertical walls have cracked insulation and could have exposed current-carrying wires. Also recipe for disaster. That has to be addressed.

Those junction boxes in the drop ceiling are above panel boxes. They serve outlets in pics 1,2 and 3. The ones I saw so far, serve front hall common area walls and are wired to the House panel box and my 1st floor unit. They would go away (good) if those common areas were serviced with new wiring.

In terms of K&T exposed wire runs, besides basements and attics, what is the likelihood that in these old homes they ran K&T in horizontal areas between floors, like 1st and 2nd fl, or 2nd and 3rd fl? b/c I see a lot of knobs in the attic that are dead.

 

K&T wiring is a given if you have 1st floor ceiling lights and wall switches. If you are relatively certain the wiring in outside walls is not K&T, why not switch to blown in cellulose insulation and cellulose attic insulation? Cellulose doesn't encapsulate the wiring or any junction boxes that may be there like foam insulation would and it would be a heck of a lot cheaper too. There are some good applications for foam insulation, but I don't think this is one of them.

 

You don't want to encapsulate any K&T with any type of insulation.

If the foam is closed cell, then there will be a higher R value than cellulose. While I think cellulose is good for retrofit, it won't get into the knooks and crannies the way foam can.

 

Very true, but we do not know if any junctions boxes exist in the attic. Since a good portion of the house has been rewired, my guess is that there are junction boxes in the attic. Junction boxes can be covered with blown cellulose, but they cannot be covered with foam.

 

I spent good portion of the day in the attic, cleaning old crap, and remnants of old roofing shingles and joists from when i had the roof done. Btw, found newspaper pages from 1853, and some prescription bottles from a pharmacy from 1883. Written in ink. Bunch of other old stuff. The attic has about 5 feet height on a mansard roof.
Instead of blowing cellulose or foam, would it be worth it to just buy rolls of fiberglass insulation and lay it between joists face down, maybe double them up. Then use 1-part can foam to fill cracks around chimney and edges where rolls don't quite meet?

In terms of K&T, i found 1 vertical run of wires that terminated in 1 ceramic pair of knobs that was live. But the wires were cut off and not used for anything. All other K&T were just sections of dead wire. Location of the two live Hot wires in the attic was vertically aligned with pic 2 location. So two of those 10 wires in pic 2 were the two Hot ones in the attic. About 6 out of the 10 in the pic 2 were live wires. That tells me that the rest are terminating into horizontal K&T on 2nd and 3rd floor. The funny thing is I turned off two 15A breakers on the main "house" panel, they are the ones that feed those junction boxes with old wires in pic 4, and of course all the wires in pic 2 were still live. But none of my lights and wall plugs went out. It seems there are sections of wiring connected to the panel, just left in the walls, but not feeding any outlets or loads. That's comforting since I can get rid of those breakers, but worrisome in terms of what else is in the walls.
Can anyone recommend a good scanner for live wire in the walls? Heck I might need the radar type with the screen to see whats in the walls.

 

We still don't know where you are located so we can not speak to your building and electrical codes.

It is my understanding that no part of knob and tube wiring can be insulated no matter what type of insulation. The wire connections they made can develop corrosion which causes resistance causing the wire to heat up. Surprisingly it's sorta OK if the connection and wire is in open air where it can remain cool. If it's insulated there is a greater chance it will get hot enough to ignite the wood framing.

You mention that you found hot knob and tube wiring but that it was not feeding anything. That's another wiring problem that needs to be corrected. You should have none, zero, nada, nothing knob and tube hot. If it's hot it's go.

I normally find it easier to just rewire everything. Some of the things they did long ago make no sense in the modern world so it can be hard to understand how the wiring is run. Then throw in probably 3 or 4 half way re-wiring projects over the years and you end up with a mess that's difficult to trace. In a house that's uninsulated it can be surprisingly easy to use the old wires to pull new wires on vertical runs. While at it you can also replace the panel with modern circuit breakers. Circuit breakers with the confirmed removal of all knob and tube may get you a lower home insurance rate because you've reduced the chance of a fire.

 

I am in Rhode Island. Panels are all breakers, looks relatively new, Square-D, 80s and 90s. I bought the house in 2001 and all the panels were already updated with breakers. Thanks for the insurance tip, I'll get a hold of my agent and see if they offer any discounts .