I have plans for a home that will have single skin SIPs panels installed above a 2×6 roof decking. The underside of the decking will be ceiling. On this ceiling will be installed a couple of fans and several lights which will require the appropriate wiring. Does code allow the wires to be sandwiched between the foam of the SIPs panels and the decking or must I run the wires thru conduit first? The SIPs manufacturer recommends simply stapling the wiring to the deck and laying the panels on top of them.
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There may be some specific rule to the contrary, but generally, if the wire is a certain distance (I'm thinking 1.25") from both surfaces then you don't need conduit (except in Chicago).
If you just fur the SIPS up with a 1x nailer over your decking, you would give yourself enough space to run conduit to all your locations.
That would limit you to 1/2"
That would limit you to 1/2" EMT.
Thermal consideration
I am thinking there may be the possibility of the wiring heating beyond their thermal limits that would require them to be installed in conduit.
I'm trying to remember what the NEC says on cable that is fully enclosed. I know there are limits of a few inches for multiple cables through the same hole, but I don't think there's any limit for a single cable, separated from any neighbors by a few inches.
If the underside of your SIPD roof is anywhere near 90 degrees C, wiring is probably the least of your concerns.
Heat is an issue inside a cable tightly bound together, as in Conduit or a chase. One cable, no worries.