Insulating around electrical wires

[Tracs]

When installing fiberglass insulation into a stud cavity with wires running horizontally, what works better:

Splitting the batt so half is behind the wire and half is in front

Or

Making a slit in the batt with a knife and pressing into stud cavity.
And if this method would the slit be better on the back side of the batt, or the front with the batt pulled behind the wire so the slit facing into building.

 

[mike93lx]

Won't matter as long as the cavity is as full as possible with the insulation as uncompressed as possible. Do whichever you find easier

 

[908Jim]

Slit the back and slip over the wire. If you are using fiberglass with Kraft paper vapor retarder, you want to keep the vapor retarder layer in tact. I doubt it matters if you're using unfaced insulation. When you put it in the stud cavity it should close itself back up anyway.

The most important thing is making sure the insulation is full expanded and the back and sides make contact with the stu cavity. I've seen "professional" jobs where it's bunched up as it is stuffed in leaving air gaps. Also, doesn't hurt to use a marker to quickly draw on the Kraft faced insulation where you've got a wire running across in case somebody in the future opens up the drywall for whatever reason.

 

[Stuart in MN]

I split the batt in half, but think either way is fine.

 

[Skooterj]

I don't think it will matter much which way you do it, but I know if the wires are anywhere except the end of the batt that I'm going to just make a horizontal slit. No way I'm going to make a 4 foot vertical slit to slide over and behind a wire.

 

[Stuart in MN]

Splitting the batt into two layers requires no tools, and takes about one second to do.

 

[Tracs]

The insulation is unfaced and I will be installing a poly vapor barrier over the insulation as is the style here.

I did a few cavities by splitting the batt into two it's not overly hard. I may try a slit to see if it is easier.

I just didn't want to choose one way or the other if one was better.

 

[NUTTSGT]

I'd guess, 6 of one and half dozen of the other...

 

[cmandp]

Depends how far from the end of the batt the wire runs. If it's close to an end just split and tuck some behind. If it's in the middle you're not tucking 4 feet behind it. In that case cut approximately where the wire runs and tuck a small flap behind the wire.

I have been using Rockwool exclusively instead however since it's just nicer to work with. But the process is about the same.

 

[Tracs]

Depends how far from the end of the batt the wire runs. If it's close to an end just split and tuck some behind. If it's in the middle you're not tucking 4 feet behind it. In that case cut approximately where the wire runs and tuck a small flap behind the wire.

I have been using Rockwool exclusively instead however since it's just nicer to work with. But the process is about the same.

The wire is in about the middle of the 2x6. Last night I tried spiting the batt and slicing the batt. I'm not sure what one I like better. With the split sometimes it would get caught on nails/screws making it difficult to pull 2 feet behind the wire.

I think I might stick to making a slit on the backside. I just don't want to screw it up and have a gap in the insulation where the wire fits into.

I thought about rockwool but there was a $3000 difference between fiberglass and rockwool.