Insulation, Radiant and Vapor Barriers - Very basic insulation qns

I'm remodeling my kitchen and am about to reach the step of restoring my insulation. Here's my dumb questions:

1. I hear it is important to avoid gaps in vapor barrier. Does this mean that when one end of a batt of fiberglass insulation is touching another, the kraft paper vapor barrier of the two should be taped together or something? If so, what kind of tape or glue? (Don't most kinds dry out and lose their stick eventually.)

2. There's also an outside wall with fiberglass, then kraft paper vapor, then plastic sheet barrier, then the drywall. How do I re-seal the kraft paper and plastic that I had to cut in order to get inside the wall to run wiring? Is ordinary duct-tape good enough for township insulation inspections?

3. I assume I have to bring the attic insulation over the kitchen up to today's standard R-value for re-insulation work. Which takes priority: The electrical requirement that electrical wires shouldn't be covered with insulation (so they don't overheat) or the inches of insulation needed to reach the desired R-value? The electrical cables up there are pretty tight and the required thickness of fiberglass insulation will definitely get compressed by the tight cables.

4. One wall is semi-exterior (the back side of an unheated furnace closet that has a vented door to the outside). The condo's electrical box is in this wall. I assume I need both kraft paper and plastic vapor barriers. Should my fiberglass and kraft paper be pushed behind the electrical cables, or should I put half a layer of fiberglass behind and the other half in front (kraft paper, then plastic, then drywall)?

Thanks,

Craig in NJ

1. You are correct that there should be no gaps in the insulation or vapor barrier. If you use tape it should be vapor barrier rated. You can buy this tape at home improvement stores. Vapor barriers are rated with either 1 perm or less or SP-15. You will see this on the product.

2, You don't need to tape the kraft paper provided you tape the plastic with a qualified vapor barrier tape as mentioned above.

3. I would check with your local building inspector. I never heard that you could not insulate over Romex. Also I have never seen or experienced a problem with doing so.

4. Here is where I would not recommend insulating because this is an electrical box. Unlike Romex, this box has ports that may allow condensation from outside the box to enter it. If you can, I would recommend insulating the wall from inside the furnace room and covering the insulation with a fire rated material like certain sheet rock. In this case I would also recommend you use rigid board insulation. Just remember there are a whole bunch of wires in that wall, so nailing and/or screwing into it, you must be careful.

Thanks for the reply.

I wasn't able to find vapor barrier tape at Home Depot, except for an expensive role of stuff that is only meant to be used with tyvek vapor barriers. I made do with duct tape -- the adhesive won't last forever, but it'll overlap enough to be sufficient, and the kraft paper of my batts overlap a little anyway. ... That's for the attic where there is no plastic layer. I appreciate not having to worry about the kraft paper layer on the exterior wall, given the plastic is sealed. (Again, I'll have to resort to duct tape and hope that it'll hold together just from the pressure of the fiberglass.)

The insulation inspector said that wires running through insulation isn't a problem. (I guess the electrical code requirement that was confusing me said wires can be laid on top of insulation as an alternative to stapling it to the middle of framing. I can imagine it could still be a good idea to keep the wiring away from the kraft paper layer if possible, though.)

I'll keep in mind your electrical box wall advice. It isn't accessable from the "outside" of the wall -- there's a furnace/AC until shoehorned in there. Can't even get to it from the side wall since that is where my downstair's neighbor's wiring runs through.

Thanks,

Craig in NJ