New House Wiring in Attic + Conduit
If you're running the wiring along the floor of the attic; or within 7' of the floor, you'll have to protect the wiring within 6' of the point of access. Unless the attic is accessible via a permanent staircase or ladder, then you'll have to protect the wiring run across the floor (or within 7' of the floor) throughout the entire attic.

I've quoted the actual code on this elsewhere on the site