Insulation thicknesses vs. low-pitched roofs

[Konrad]

The question I'm posting is sort of third-hand, I wasn't actually there for the conversation. But here goes:

My buddy who lost his house in Hallam was looking at some of the modular homes. Apparently one of the rep's stated that on lower-pitched roofs, they don't necessarily recommend going with the full R-40 insulation above the ceiling. Possibly something to do with vapors? Climate is Midwest (Nebraska).

I'm not sure what the actual conversation was, but does anyone know what this guy might be talking about?

[Chad Fabry]

I'd want the roof as cold as possible.

[Konrad]

Yeah, me too.

I'm taking our skid loader down to Hallam today to help him demo the remains of his garage, I'll ask him again what this guy was talking about.