It's been a while since I've had to ask a question here, now that I have retired from the EC business. (and my other job as a Civil Aviton Inspector as well - it's nice to get older and retire).

However, once the neighbours know about your past, I get questions and asked for advice about electrical installations. One of them has me flummoxed since I had not run into this one before.

He is doing a new basement installation to add a new living space in the basement and the 2X6 walls are being wired for all kinds of stuff including CAT 5 and every other kind of who knows what its for, cable including the basic electrical outlets, switches and fairly elaborate lighting system in a suspended ceiling system.

However there are a few places where 4 NMD 90 cables could be run up the 2X6 studs from just above the concrete floor level to the ceiling and these are on outside walls that he would like to spray with foam insulation.

I have checked both the CEC and NEC codes ad nauseum, about spraying insulation into the interior of the wall stud cavities and can find about zero information about any requirement to derate the cables for that kind of insulation. We all know about the usual batt insulation stuff but it seems to me that maybe the same rules that might not apply since there is no air flow in spray insulation as in fiberglass or rockwool insulation.

Has anyone here have information, experience or a code requirement about spray foam insulation applied on outside walls that require derating of the conductors?

Last edited by electure; 02/06/10 11:24 AM. Reason: Double Posting