I would say at least a couple of years back I bought all this un-faced insulation to put in the attic because it was on massive sale at Home Depot. I was talking to CF at the time and he said just layer it on top of the pre-existing stuff to get an extra layer insulation. It sounded simple enough, but in typical fashion I bought the rolls and they sat in the basement for two years, maybe three, past the statute of limitations of returning it... I think.
Either way, it turns out that I still need to insulate the kitchen in the barn, and the studs are 8 inches wide. It just so happens that the rolls I have are 8 inches thick, albeit un-faced. I asked several of my contractor friends and they all said it would be fine to use it in vertical walls, you just have to add your own vapor barrier, whatever that is. Good enough for me. Now the insulation won't go to waste, I already have it in my possession so I don't need to get more (at least not for now), and I clear out some space in the basement. I love when that happens. For the record, we are not for want of space in the basement, we have tons of it, but three big rolls of insulation is a bit of an eye sore.
Of course, this all sounds great in theory. Putting things into practice is a whole other story, so we'll see how it goes.
Until then, thanks for reading, and thanks to Better Business Listing for the pic.