Insulating an Old Vented Attic With Questionable Wiring
michaeldrehl
| Posted in General Questions on
Hello. I have a house in the northern NJ built in the 1900s. It has a flat pitched roof. It is a vented attic. Currently, there is no insulation. I’m trying to insulate the attic floor with blown in cellulose. The roof tends to leak every 2-3 years near where the vents are located. I put flashing cement near the joints on vents on the roof and it stops leaking.
The electric wires as pictured below run throughout the attic. I’m not sure how old they are but most of them are in that metal casing. I used to have two prong outlets in the house but I replaced them with three prongs ones a decade ago.
Do you think it is safe to insulate the attic with cellulose? After insulating with cellulose, would I notice a leak if the roof starts to leak?
Thank you!
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Replies
That looks like old AC (sometimes also called "BX") cable. The area of the cable in the lower left corner of that pic looks like it might be damaged, if it is, replace that run.
The conductors inside look like the old type R conductors, which had a fabric braid "serve" over a rubber inner insulation. DO NOT let these get wet, and note that the rubber tends to get VERY brittle on old wiring, which means if you bend it it can fracture and be a problem. The good news is the steel armor of the cable should be grounded (check that it actually is, loose fittings can cause it to not have a good ground connection), which limits the risk of fire if the internal insulation gets damaged.
You can bury that cable in insulation, but the box needs a cover. I'd prop the box up above the level of the new insulation too using a scrap of 2x4 or whatever is handy.
If the insulation in that box is heavily damaged, or if any of the armored exterior of the cable is, you'll want to replace it.
Bill
Thanks Bill. I went down in the basement for a clearer picture and here's the type of wiring that I have. I'll need to go back into the attic for a clearer picture of j box. The house has two meters and there's a wire grounded to the copper water supply line. Is that what you meant by having the steel armor of the cable be grounded?
Yeah, that's the stuff I was talking about. The old insulation was a fabric serve (the braided covering), which was cotton or rayon depending on the vintage, over a natural rubber insulation. Over time, the rubber dries out and gets brittle -- really brittle. If you bend the wire, the rubber will crack and/or crumble. The fabric serve tends to keep the rubber pieces together, but once that rubber cracks, any moisture can get in and cause a fault which will eventually cause the cable to fail. You need to be very careful with this type of wire.
The metal armor makes the cable less risky, since the metal provides a fault current path IF it's grounded. The ground connection TO THE CABLE is made through the connectors on the end, which need to be tight so that they clamp the armor securely and bite into the metal of the box they're connected to. That box then needs to be grounded. The copper wire you see is probably the ground for your electric service (make sure there is a jumper around your water meter, BTW, and make sure there are no dielectric unions between the ground wire connection point and the water pipe leaving your home.
The connector on the right does NOT appear to be clamped securely to the box. It looks very loose. That is a problem. You might be able to remove the bushing and add a lockwasher to fix that, but it looks so rusty that the old bushing might be seized. I would seriously consider replacing that run, or at least that section of cable.
What I would do is replace all of that wiring that is exposed during any renovation work I do. Note that in some areas you're required to use armored cable or conduit (the Chicago metro area is notorious for this requirement), in other areas you can use the plastic sheathed NM cable (romex). Be sure you use the correct materail for your area.
Bill
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Zephyr7 correctly described the type of cable you show in the pictures and about the grounding but I would have some addition concerns. The one cable that is referred to as damaged may be an unboxed splice, we can't see enough of the pic. Unfortunately this happens when some of the older "knob and Tube" is replaced with this type of cable. I mention "knob and Tube" because you said most, not all. Do you also have "knob and Tube" in the attic? If so do not cover it, replace it or don't insulate. As Zephyr7 said, best to replace all of this or you WILL be dealing with it again, if not here then when you try to replace a light fixture were the heat from those incandescent lamps destroyed the rubber insulation. Are the walls also without insulation? if so your job may be much easier. If replacement is not a possibility, at a minimum I would check the tightness of all those BX connections, splices, damages and fix/replace as noted above. I would have also put a GFI with feed through thru on those circuits before You replaced the 2 prong outlet because I would be very suspect that the ground was good enough to actually trip a breaker on a ground fault. I understand time and money but the alternative could be much worse.
+1 for using GFCIs, ideally in the panel.
Bill
Thank you Bill and Dennis. No, I didn't see any knob and tube wiring in the attic. The rubber on the wire seems pretty intact. I pulled out an electrical three prong outlet and attached is the picture. It seems the wire to the outlet is grounded to the metal box but the metal armor of the cable is not grounded. It was hard to see behind the metal box and I doubt it is grounded back there.
Do you think all the problems could be solved if I just install GFCI breakers in the panel? and then insulate?
Thank you!
I'm afraid that my answer is no, just installing GFCI breakers is not sufficient. That would reduce the risk for some kinds of problems but is not as good as having the wiring done right and having GFCI breakers.
It's hard to say how much needs to be done--for example, in this last picture, there was an attempt to ground the box, but it wasn't done properly. That specific problem would be a five-minute job to fix, and would be well worth doing before burying that, but there may be many small problems to the point that it's worth rewiring.
There are some good circuit analyzers available these days that cost about $300 but can give you a fairly good idea of how many of what kind of problem you have in a circuit you plug it into. That can help scope out what problems are hidden. But it's a lot easier when you can directly look at what is going on, so I think he answer is to get a good electrician to take a look.
Michael,
I know it is easy to tell others to spend money, but now would be a good time to correct the rather frightening wiring you have depicted. I spent several years upgrading a similarly aged home near Chicago, replacing all water lines and electrical wiring. And yes, I put all wiring in conduit per code. Fortunately for my budget, I could do all the work myself. My spouse disagreed with the time spent, but that is a different story.
Your desire to insulate the attic is also where I started my renovations. I also had mixed wiring that dated back to the fabric over rubber inside armored cable, mixed in early BX, and illegal NM/Romex wiring. Your first photo shows a loop of white NM/Romex that appears to be spliced into the box. Where does that wire go? Is it grounded? Is it legal? Is the circuit overloaded?
The gravest concern I have for you is continuity of ground paths and fractured wiring at overhead light boxes. Every one of the ceiling light boxes on the second floor contained failed insulation on the wires thanks to the decades of heat rising from the incandescent bulbs. The failed rubber insulation extended back into the cable leaving bare wire protected by random bits of the surviving cloth over-wrap. Through basic circuit tracing, I found most of the upstairs was all on one circuit. The previous owners had daisy-chained numerous outlets onto the original and very limited wiring common to old houses. The outlets had all been replaced with grounded ones, which did not actually have a ground path that functioned.
The original panel was 60 amp with cartridge and screw fuses. Electric demand planned for a house built in 1900 house would have been a small fraction of what we demand now. This almost ensures that many if not most of your outlets and lighting are add-ons done by unknown parties. Your second photo shows big red wire nuts and interim insulation style wires, so clearly grafting to old work has been done. The last photo you posted is especially disturbing. The wiring appears to be a rubber type popular in the 50's and early 60's and the "ground" wire is looped to ???? It is not even clear from the photo as to how the wires are entering the box. I am not seeing an appropriate connector.
It appears that the wires are just stuffed through available holes. What is happening on the other side of the box? Are you sure it is not just an extension cord that was run through the walls. I had one of those beauties. I also found four wall sconce boxes that had been papered over with no metal covers. I found them with a putty knife that fortunately was plastic. I also found a BX run between two windows that for some reason had an outlet placed half way up. The outlet was long gone, but they didn't bother to cap the wires when they re-trimmed the windows.
You mention having two meters, which in itself is odd, but I am guessing that you have one modern panel with breakers and possibly an old style one. Or maybe a former rental unit that may have an entirely separate wiring system. Our old house had a "grannie flat" that was coded out of existence, but the wiring mess lived on.
I know the cost of hiring an electrician is daunting, but the potential for disaster is not likely to be cured with a few GFIs. And you may yet have knob and tube in the walls. My carpenter friend was doing work on a house of similar age and was assured by the home owner that all the old wiring was pulled out. His sawzall found out otherwise. If you have access to ALL the rim and joist pockets, do check. It was fairly common in past decades to create jump points to "modern" wiring by covering over a pocket with wood and bringing the wires to a box where AC or BX would then be used. Boxes set onto the top plates in the attic (if framed that way) are red flag for the same reason. My house was a bastard version of balloon framing and whatever they decided that day. It did make a few of the conduit runs easier to achieve.
Sorry to be such a Cassandra.
Just to emphasize the seriousness of the potential problems, my neighbors a few doors away live in a ~1970 house with wiring much more modern than yours, and without any of the classic wiring issues from that era (e.g. poorly applied aluminum). But a problem in an outlet downstairs led to a fire that destroyed most of the interior of the house and destroyed about half of their belongings. Fortunately, nobody was home and nobody was hurt. But it probably would have burned to the ground if a neighbor hadn't seen smoke early and called 911.
Thank you all for your replies. First, I looked further into the outlet wires. I was able to get a better view from another outlet. The Armored Cable is grounded to the metal outlet box from underneath the metal box. Attached is a clearer picture. Then the outlet is grounded to the metal box.
Second, for the attic wires. I had an electrician come and look. Where the cable was damaged, the electrician cut it off and grounded it to the j box. Where the white NM wire is spliced, another j box was created, as shown in the picture.