Install new wiring in wall with insulation


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Old 07-20-05, 08:16 AM
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Install new wiring in wall with insulation

I have an 80 year old house and want to replace the knob and tube wiring. In many locations the wiring is in an exterior wall which has insulation. Can new wiring be fished through walls with insulation? If not, what do recommend for installing the new wiring through these exterior walls?
 
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Old 07-20-05, 08:32 AM
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Yes, you can fish the wire through walls with insulation. Depending on the type of insulation this may not be an easy task, but it can be done.

However, there should not be insulation with knob and tube. Those two do not play nicely together. They get into a heated argument so to speak.
 
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Old 07-20-05, 08:43 AM
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OK thanks - I know I have knob and tube wiring and I assumed the exterior walls were insulated but I will double check.

If the walls do have insulation, is fishing the wire through the wall the same basic philosophy as no insulation? I suppose you try to keep the fish tape between the insulation and the plaster wall?
 
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Old 07-20-05, 08:56 AM
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The type of insulation make a big difference.

A house with knob and tube likely was built with no insulation. If any was added, it was likely blown in. With blown in insulation you just want to make sure that you don't lose much of the insulation when making holes in the walls. If there is insulation with a vapor barrier, your objective is not to destroy the vapor barrier. Yes, you have to make cuts in it, but you don;t want to rip it.
 
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Old 07-20-05, 08:58 AM
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Yep, or use something more rigid to get through the insulation. One of those really long spade-type drill bits might be useful; it's basically a spade bit with a 4-6 foot flexible metal shaft that usually has a pull hook built in also. Romex NM cable is often rigid enough to not need a fish tape at all, just run it into a wall space and reach through the box hole until you can feel it.
 
 

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