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Electrical wiring in insulated attic

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  • Aug 25th, 2021 8:19 am
[OP]
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Oct 4, 2020
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Electrical wiring in insulated attic

Hello guys,

I’m trying to add some IC rated LED recessed lights on the ceiling. Need to run some wires in the attic for these lights. My question is, where should I put these wires?

1. under the insulation next to the ceiling drywall?
2. In between the insulation?
3. Above the insulation?
4. Or it doesn’t matter?

Found some pictures online, looks like the wires are everywhere Slightly Frowning Face
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9 replies
Deal Addict
Nov 9, 2008
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Toronto
In an attic, didn't really matter. Half my potlights are run along the rafters and with holes drilled to pass them through between the bays.

The other half are just jumped up and over the rafters and insulation.

You don't go up there frequently and no one walks up there, so shouldn't really matter.
[OP]
Newbie
Oct 4, 2020
20 posts
3 upvotes
jacquesstrap wrote: In an attic, didn't really matter. Half my potlights are run along the rafters and with holes drilled to pass them through between the bays.

The other half are just jumped up and over the rafters and insulation.

You don't go up there frequently and no one walks up there, so shouldn't really matter.
In the summer, the attic space is pretty hot, it can be as hot as above 60 degree C. Will those wires be ok? The house is a bungalow built in the 70s, I saw my kitchen counter plug wires are also running along the joist, is the attic too hot in the summer for these wires when i'm running some heavy appliances?
Deal Addict
Jun 8, 2004
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Oakville
Where's the vapour barrier?

Ideally, I would have thought the vapour barrier would have been tacked to the underside of the joists and then the drywall screwed into the joists, sandwiching the VB between, then the insulation on top of the VB. Now it looks like the VB has to be installed on top of the joists which makes it a lot more difficult, not to mention on the wiring now in the way of laying the VB.
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Jun 21, 2003
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Stoney Creek, ON
jacquesstrap wrote: In an attic, didn't really matter. Half my potlights are run along the rafters and with holes drilled to pass them through between the bays.

The other half are just jumped up and over the rafters and insulation.

You don't go up there frequently and no one walks up there, so shouldn't really matter.
This is bad advice. It is NOT to code to run atop the joists/under rafters unless the space between them is less than 1m.

Here is the Canadian Electrical Code rule for reference.
12-514 Protection on joists and rafters (see Appendix G)
Cables shall not be run on or across
a) the upper faces of ceiling joists or the lower faces of rafters in attic or roof spaces, where the
vertical distance between the joists and the rafters exceeds 1 m; or
b) the lower faces of basement joists, unless suitably protected from mechanical damage.
Run your cables along the sides of the joists and drill through joists whenever you need to pass from section to section. Make sure to drill in the middles of joists when going through them.
ftaman99 wrote: In the summer, the attic space is pretty hot, it can be as hot as above 60 degree C. Will those wires be ok? The house is a bungalow built in the 70s, I saw my kitchen counter plug wires are also running along the joist, is the attic too hot in the summer for these wires when i'm running some heavy appliances?
NMD90 which is the wire you need to use is rated for 90 degrees. There is no issue at all and every home you go in you’ll find this in the attic. It is absolutely acceptable.
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Aug 5, 2003
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ChicoQuente wrote: This is bad advice. It is NOT to code to run atop the joists/under rafters unless the space between them is less than 1m.
....
Run your cables along the sides of the joists and drill through joists whenever you need to pass from section to section. Make sure to drill in the middles of joists when going through them.
How often are rafters more then 1M apart - I don't do construction but isn't the standard every 16-24" (so well less then 1M)
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Jun 21, 2003
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cliff wrote: How often are rafters more then 1M apart - I don't do construction but isn't the standard every 16-24" (so well less then 1M)
We’re talking about vertical clearance (top of joist to bottom of rafter) not horizontal spacing. The CEC views 1 metre clearance as sufficient height that someone could walk under there and step on cables. Once the location marked by a blue arrow in the attached photo reaches 1 metre you can no longer run cables on top of the joists, you must go through them.

Also sorry for the crappy arrow but I am just on my phone.
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Deal Addict
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Aug 5, 2003
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North York
ChicoQuente wrote: We’re talking about vertical clearance (top of joist to bottom of rafter) not horizontal spacing. The CEC views 1 metre clearance as sufficient height that someone could walk under there and step on cables. Once the location marked by a blue arrow in the attached photo reaches 1 metre you can no longer run cables on top of the joists, you must go through them.

Also sorry for the crappy arrow but I am just on my phone.
Ah, that makes sense, didn't think of that aspect

Thanks,
[OP]
Newbie
Oct 4, 2020
20 posts
3 upvotes
ChicoQuente wrote: This is bad advice. It is NOT to code to run atop the joists/under rafters unless the space between them is less than 1m.

Here is the Canadian Electrical Code rule for reference.



Run your cables along the sides of the joists and drill through joists whenever you need to pass from section to section. Make sure to drill in the middles of joists when going through them.



NMD90 which is the wire you need to use is rated for 90 degrees. There is no issue at all and every home you go in you’ll find this in the attic. It is absolutely acceptable.

Thanks for the advice. I found 2 pictures online. Just to confirm, basically the way they run in picture A is bad, and I should run it like picture B? However if I cover these wires in the insulation, will that be ok?
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Oct 19, 2008
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ftaman99 wrote: Thanks for the advice. I found 2 pictures online. Just to confirm, basically the way they run in picture A is bad, and I should run it like picture B? However if I cover these wires in the insulation, will that be ok?
A is ok because there isn't enough height to walk there. The wire is fine covered in insulation either way.

Also most ESA inspectors will consider the wire fished in attic so no staples required etc, installer can work through pot light holes without going into attic.

Pic A is actually an attic; pic B isn't.

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