Good question, Markp, about the 1/4" airspace for LFNC. I quess when I read 300.6(c), it's not clear to me that they are referring to just metallic materials: "...the entire wiring system, where installed exposed, including...all conduits and cable, shall be mounted so that there is at least 1/4" airspace...." That sounds to like even UF cable would require the airspace. You think maybe I'm misinterpreting?
As for the possibility of using UF, I would love to go that simple route, but I'm afraid "subject to damage" might be an issue in this greenhouse. It's a very dynamic space, with an upper deck and waterfalls, etc., plus constant digging and planting. Not your ordinary retail greenhouse, but more of a personal botanical garden.
RNC is probably the best way to go, though "easy to bend" doesn't exactly fit my experience. I haven't yet wanted to shell out the bigbucks for a heating blanket and so have made do thus far with a heat gun: SLOW!!!
