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As part of renovations to our home we chose to replace existing aluminium electrical wiring with Copper wiring. We also wanted to replace the original R7 insulation with something better (R14 or 15) to minimize heat loss.

The issue we have now is that with the walls open the contractor has run a whole bunch of wiring through the wall studs. This poses a challenge with how to properly insulate the walls. We are concerned the insulation may not properly fit into the space and I understand we need to be careful that the insulation does not get compressed which will compromise the R value.

Hoping the experts from the forum can suggest how best to handle this scenario. Thanks for all the help with our questions!

EDIT - updated photos below. Not sure if this addresses some of the concerns about wires not being properly secured.

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  • Is continuous exterior insulation an option for you, or are you not touching the cladding of the house? – ThreePhaseEel Oct 23 at 0:44
  • Hi there - sorry but we are not touching the exterior brick cladding. Thx – user105375 Oct 28 at 21:00
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That's... artsy-looking wiring. I believe the stapling or lack thereof doesn't meet code. We should give due credit though for not jamming all those cables through as few holes as possible.

In any case, you asked about installing fiberglass insulation around the wiring. In the case of cables that fit neat and tidy against a wall stud, as do the three white and one yellow starting at the top left, simply install the batts and don't worry about it.

Cut away insulation so that it fits neatly around junction boxes.

Where cables pass through the middle of the depth of a bay separate the batt halfway through its thickness. Slide part of it behind the wiring and lay the other part in front. This minimizes the compression of the batt. It would also be possible to make cuts in the batt so that the batt can expand around the cable, but if you're using faced insulation it's best to avoid cutting the facing.

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Gosh! That sure is a lot of wires.

Several ideas come to mind: Spray foam, extended wall, and work around them.

Assuming that is an exterior wall in a cold or warm climate where insulating is of great value, first secure the wires per NEC (within 8 inches of a box or hole and at least every 4.5 feet), then (probably via a contractor) spray insulating foam to bring it up to the desired insulating value.

Increase the wall thickness in that area (or the whole length of the wall for better uniformity), such as adding another 2x4 thickness to bring the wall thickness to 7 inches (2 times 3.5 inches) which would nicely accept R-19 with a little TLC around the wires.

Or if R-11 (or R-13) is acceptable, split the batts as Greg Hill mentions and install semi-normally.

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That. That is why I do EMT conduit. That would be 8 pipes in my world (3-4 circuits per pipe for a little expansion room without esceeding the 310.15B3A derates).

Remember you must have that wire be roughly centered on the 2x4 walls. You must not have a situation where driving a 1-5/8" fastener from either finished surface has a chance of nicking a wire.

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