Do I need exterior grade cables or conduit to run wire in an enclosed soffit?

Question

I'm looking to add some lights on motion detectors (un-switched) and security cameras under the eaves of our house. I know standard romex is often used in attics, but the soffits seem like they might be more exposed to weather. Our soffits are enclosed, like so: (picture from wikipedia.org)

So, do I need to protect any wires which reach into the soffit, such as would power the pictured light? Or should I use wire rated for exterior use? I'm also plotting some Cat 5e runs of a similar nature, should those be protected/exterior as well?

Answer 1

While soffits usually have some venting in them, the interior of soffits are interior spaces not much different from unfinished attics to which they connect. Attics do not require different wiring from other interior spaces, so it doesn't seem that soffits should either. While attics (and basements) may often be more humid than some other spaces in a wiring scheme, these do not pose significant problems for normal interior cabling and outlet boxes.

The fixture illustrated has a weatherseal around the base (as do all exterior fixtures) to keep water from infiltrating. On the other side of that seal, no liquid water should be present.

It seems likely that the same applies to CAT5e cabling. However, as has been discussed elsewhere, fire rating of low voltage cable is an issue. Use properly rated cable.

Answer 2

I'm no expert, but I'd use internal rated cables. The exterior grade stuff isn't necessarily 'more weather resistant', but rather the interior stuff is safer in case of a fire (the insulation around the wires doesn't produce anything toxic when burned). Since it's under the roof, I'd want the same stuff that it's in my walls.