wiring question

Discussion in 'Shop Talk' started by .netDude, Nov 16, 2006.

  1. .netDude

    .netDude Well-Known Member

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    When running wire through ceiling joists, do I rest the insulation that I put up on the wire, so the wire is against the foil side of the insulation, or do I run the wire 'under' (really over, since it's on the ceiling) the insulation so it's next to the fiberglass part?
     
  2. Gideon

    Gideon Well-Known Member

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    Is it a two story or single? If a single story I would not drill holes in the joists but attach them on top. wc
     

  3. Yeti

    Yeti Well-Known Member

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    I am wondering what type of use you are doing foil insulation on?
    foil is a heat reflector and does not let vapor move freely. ceilings should not have a vapor barrier because it will cause them to sweat. it will cause mold and other deterioration problems if used behind drywall. if you are using it in a barn or garage where there is nothing to interfear with it then it would be ok. I am just concerned its being used improperly
     
  4. dennisjp

    dennisjp dennisjp

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    Keep the foil side down, toward the living area and run the wires on top of it. And yes, do use insulation that has a vapor barrier. That is what it was invented for.
     
  5. .netDude

    .netDude Well-Known Member

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    Thanks for the responses. It's a single story, but on top of the joists is existing plywood, so I can't run the wires on top. I'll pull the insulation down a little and feed the wires above it. As for foil, that's what was there,and all of the insulation I've seen in the house has this. (not saying it's right or wrong, just an obesrvation)
     
  6. The Paw

    The Paw Well-Known Member

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    Where I live, you couldn't run the wires on top of the joists if you wanted to meet code. The theory is that you could pinch the wire between the joist and something else (boot, plywood, etc.) and compromise the insulatation.

    If you are talking about fiberglass insulation with foil backing, the foil goes to the warm side, in order to act as vapour barrier.

    When I re-did an old house, I drilled holes through the middle of the joist, and I would peel back the layers of the fiberglass so that the wire could go through the middle of the batt. (some insulation below, some above). That seemed to work well.