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Old 04-13-2010, 10:16 PM   #1
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new ceiling bat insulation with old attic wiring


I'm looking to install new r30 bats over exhisting(looks orgional) '61 (romex I think)wiring. Is this a fire hazzard? They are layed on ceiling joists without being in conduits. Is this normal?


Last edited by 1961fixer; 04-13-2010 at 10:33 PM.
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Old 04-13-2010, 10:29 PM   #2
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new ceiling bat insulation with old attic wiring


What type of wire ?

NMB (romex), single wires, knob & tube wiring ?
Pics ?

Romex is fine to lay across joists
I usually will try to put boards up to walk on so that I do not step on the wires & do not go thru the ceiling

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Old 04-13-2010, 10:33 PM   #3
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new ceiling bat insulation with old attic wiring


If the wires are on ceiling joists, wouldn't the new bats go under the wires, rather than over? Do you actually plan to place the insulation over the wires?

If you think it is romex, then it could be normal to lay on joists without conduit. Assuming it is a NM cable.

Last edited by jlmran; 04-13-2010 at 10:35 PM.
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Old 04-13-2010, 10:56 PM   #4
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new ceiling bat insulation with old attic wiring


That begs the question, why can't i run batts over the 2x3 joist trusses lon g ways? it seems it would be a lot easier to cover over both wires and the plastic replumbed water pipes if its safe to? I'm in FL so freezing water isn't a problem.
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Old 04-13-2010, 11:00 PM   #5
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new ceiling bat insulation with old attic wiring


You've transitioned from ceiling joists to trusses. I think I may be confused about what you're attempting.

If you're talking about covering everything with the bats (joists, wires, pipes, etc.) then you might consider SubaDave's comment above. If you cover the joists, then you might not know where to walk in the future. Might end up with a shoe-full of sheetrock if ever you need to enter the attic.

Last edited by jlmran; 04-13-2010 at 11:05 PM.
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Old 04-13-2010, 11:09 PM   #6
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new ceiling bat insulation with old attic wiring


They are both prefab roof trusses in the low pitch attic and my ceiling joists. It's only 3 or 4' inside at the ridge.
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Old 04-14-2010, 12:01 AM   #7
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new ceiling bat insulation with old attic wiring


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Originally Posted by 1961fixer View Post
They are both prefab roof trusses in the low pitch attic and my ceiling joists. It's only 3 or 4' inside at the ridge.
prefab roof trusses from 1961??

You might want to take a picture and post it, it would give readers a clearer picture of what you have.
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Old 04-14-2010, 01:11 AM   #8
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new ceiling bat insulation with old attic wiring


You CAN go over the wires and plumbing with insulation, but ONLY if there is insulation underneath the wires already.

Insulation will NOT work if there is an air gap between the wall surface and the insulation.

What I did in my attic was I laid down 6" insulation inside of the joists underneath the wiring and plumbing. Then I went back with a second layer of insulation in the opposite direction on top of the joists and wiring.

After I did all that work, I realized that it would have been MUCH easier to just blow loose cellulose insulation into the attic.
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Old 04-14-2010, 08:12 AM   #9
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new ceiling bat insulation with old attic wiring


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Originally Posted by Shrute View Post
Insulation will NOT work if there is an air gap between the wall surface and the insulation.
I would have thought that the air gap (without cracks between batts leading to the outside) would not make any difference and might even increase the insulating qualities provided that the insulation batts were fluffed to the same thickness (not squashed where they passed over the wires).

There should not be insulation between water pipes and the inside wall surface even if you do have to squash the insulation batts in the remaining space behind the pipes.

Now I never understood why knob and tube wiring could not be surrounded by insulation given the same gauge wiring and same electrical usage (load) as for Romex cables run through the same insulation.
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Last edited by AllanJ; 04-14-2010 at 08:16 AM.
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Old 04-14-2010, 08:21 AM   #10
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new ceiling bat insulation with old attic wiring


Insulation is installed in a ceiling before it is sheetrocked
Then strapping is run across the rafter joists & sheetrock is added
This creates an air gap & the insulation still works

But you are better off without an air gap, especially as large as 2.5"
Best to fill the lower area 1st, then add more on top

Several states have OK'd insulation w/knob & tube
There are requiremsnt - usually an electrician has to inspect & approve the K&T 1st

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