Junction box in attic covered by vapour barrier


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Old 05-16-09, 10:50 AM
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Junction box in attic covered by vapour barrier

Hi,

I'm attempting to replace old knob n tube wiring to my 2nd story. The attic is unfinished, but from the top there are thick batts of insulation, more thinner batts, then between the joists is vapor barrier, then blown insulation - this is the zone where the existing wires are.

I believe it will be necessary to use junction boxes to accomplish my task (otherwise the light boxes and switches will be overburdened). Can i put junction boxes in that zone? I know you can't cover with plywood (as seen in another post), but does vapor barrier and a lot of insulation mean that it is still accessible?

Thanks,
Bob
 
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Old 05-16-09, 11:07 AM
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yes, they are still considered accessible. They are very difficult to find though.

I have better luck by running the wires up to where the box would be not only accessible but visible as well.
 
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Old 05-16-09, 11:47 AM
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Just to add a bit: I presume you are replacing the K&T and already know it can not be covered with insulation.
 
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Old 05-16-09, 11:52 AM
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Ok thanks. You mention putting the box where its visible and accessible - where would that be? My attic is just insulation, do you mean put it outside the insulation zone in the cold area of the attic, say on one of the roof trusses? that is a possibility but i didn't think that was allowed either.

As for the K&T - i'm removing all of it, and for the record it was completely covered in insulation. I don't sleep well at night knowing its there, so i'm getting rid of all of it. So it was covered, but no longer exist, therefore not covered Let me know if you think i'm misunderstanding.
 
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Old 05-16-09, 11:56 AM
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No, you understood me. No need to remove though. Just cut at both ends and abandon if you want to.
 
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Old 05-16-09, 12:05 PM
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Yes, mount the box on a chord of a truss or on the rafter or any available mounting point. It must be supported and secured within 12 inches of any box and every 4 1/2 feet there after.

If running it perpendicular to the ceiling joists, you need to protect it with running boards so it will not be crushed where it crosses a rafter. This is required within 6 feet of an access hatch. There are rules as to where this is applicable but the easiest method to remember is; if it is where it may get stepped on, guard it.

The NM is to closely follow the framing members (which means it can't simply be run willy nilly and hanging everywhere.)
 
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Old 05-16-09, 02:25 PM
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It sounds like your vapor barrier might be in somewhat the wrong place, as it should be on the warm side of the insulation, next to the drywall. Not sure if you want or can change it, but make sure any new holes you drill and any old ones you find, you seal them. Air that leaks up under a vb can cause condensation if it can get close enough to the cold.

Good luck
Bud
 
 

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