Vapor barrier and A/C

I have come across some mobile homes with no vapor barrier at all. There is vinyl siding, osb, unbacked fiberglass insulation and 1/4" sheetrock. No Felt, Tyvek or plastic barrier. I know Mobile homes a built cheap but what a place to cut costs on. Am I missing something?



By the way, what is the correct way to install fiberglass insulatrion these days? It used to be with the paper on the inside, but some houses used unbacked insulstion in places.



Confused, as usual.