Running Electrical Wire through insulation

Hello, I’m back with another question. Everything a read is telling me yes I can, but it really does not feel right so I’m gonna ask here for good measure. Can I run electrical wire through fiberglass insulation?

In several rooms upstairs the wire comes out of the center of the ceiling then goes across to the window where a fluorescent tube light is installed. Below all that is a drop ceiling tile with insulation packed on top of it. I want to take the fluorescent light out and put a normal light back in which is easy enough. My concern is running the wiring through the insulation. Everything says running it through insulated walls is fine and the insulation itself says it’s non-combustible. But can someone confirm that I’m reading the right stuff?

There’s a gap between two pieces of insulation that I want to run the wire between. Picture attached. Not sure how old the insulation is if that is important.

SubArcticTundra, avatar

I know this insulation is fine but just watch out for asbestos, I don’t know how old your house is


Ya, there is asbestos in the house. It is wrapped around the HVAC in the basement. We were told to get it removed now because it’s not yet a health hazard so I’m working on getting that done. It’s still in good condition and it’s not dangerous until it starts to flake away. But the insulation is newer from a remodel when the last owner turned it into a duplex. So within the last 10 years I am pretty sure


If it helps any fiberglass isn’t called that for funsies. It’s actually made of glass fibers in a resin. It’s not any more flammable or conductive than any other kind of glass/resin combination. The most important safety advice for using it is to wear gloves and protective glasses, because having lots of tiny glass fibers break off in you is super itchy, and your hands are right up in there, and itchy eyes are just the worst.


I knew it had glass in it but I wasn’t sure if that’s all it was made of. That and the paper backing just made me want to be cautious. But I do know how to handle insulation from tearing a room off my grandparents house a few years ago.


Modern insulation is basically fireproof and the probability of just cables causing a fire is pretty low nowadays as well.


Regular modern romex wire is fine.

You can’t insulate over old knob and tube since the cloth insulation degrades and flakes off.


Tell that to the maniac who wired my house 95 years ago.


The guy wiring with knob and tube was probably not the maniac who put insulation over it at a later date.


AFAICT it was all done in a four-year period from 1926 to 1929 and untouched until I ripped the ceiling open in 2018.


This is thankfully not knob and tube. The house is old enough for it though. Going in the attic you can see where the wires used to run


If everything you have read is saying that it is fine, then why does it not feel right for you? Looking around I do get the same impression, it is non-combustible so there is not really a concern there. Basically from what I gather as long as you use the proper wire for use in walls/isolation, leave enough space and generally take good practices in account like using conduit where needed you should be good to go.

I am not an electrician though and certainly not aware of your local code and regulations.

Talking about electricians, if you are worried about doing it not right, why not hire one to do it for you?


I’ve been through 6 electricians and 3 general contractors. Probably more but I can’t keep those numbers straight. They all show up to give a quote then never actually do the work. I’m tired of it.

That being said, the insulation just feels flammable to me. It’s clearly marked otherwise but the paper backing and stuff just made me want to double check


Romex on a 15A breaker is simply not going to get meaningfully hot, even under worst-case scenario loads and even fully insulated in something entirely flammable. If you're very nervous, size it up to -- it will cost slightly more but be even more totally safe. Overbuilding is (should be) the DIYer's creed.


12/2 is what I bought for the basement lights I’m working on. Everything I read said that was the appropriate wire to use so I never even co sidered


Make sure you’re buying 14/2 or 12/2 that has a ground wire and running that back to the breaker box. I saw the job you did with the big cable in the floor and it didn’t look like you ran a new cable that had a ground wire. It’s best to replace the old shoddy stuff with circuits that are up to code, even if you’re doing it DIY and your area doesn’t require homeowners to get it inspected. The codes are designed to prevent fires and loss of life.


That was a 240v circuit. It didn’t have a ground because it was 10/3. I had the money to get the stuff with a ground, but they were sold out and I couldn’t get anything for a few weeks so I went with the no ground but it is still up to code and manufacturer approved.

This does have a ground and black is going to the breaker with white and ground going to the ground bar.


white and ground going to the ground bar.

This is the main panel, right? If it is a sub panel, it is a meaningful shock hazard to have neutral and ground bonded together.

downpunxx avatar

"measure twice, cut once", you're absolutely doing the right thing by sounding this out with your doubts and asking for input, then making a more informed decision

  • All
  • Subscribed
  • Moderated
  • Favorites
  • rosin
  • DreamBathrooms
  • tester
  • magazineikmin
  • everett
  • Youngstown
  • slotface
  • thenastyranch
  • mdbf
  • cubers
  • ethstaker
  • tacticalgear
  • kavyap
  • InstantRegret
  • bokunoheroacademia
  • osvaldo12
  • lostlight
  • khanakhh
  • Leos
  • cisconetworking
  • modclub
  • Durango
  • GTA5RPClips
  • relationshipadvice
  • anitta
  • normalnudes
  • HellsKitchen
  • sketchdaily
  • All magazines