crawl-space insulation: faced or unfaced?

[nereo]

I'm insulating the floor of a utility room from the 'crawl space' (not much crawling, since there's about 5' between the dirt floor and floor of the utility room overhead). 
I've gotten conflicting advice about whether to use faced or unfaced insulation - with no explanation as to why. 

I understand the facing provides a vapor barrier, but what I'm unsure about is whether I need one or not.

There is zero change of any rain, snow or ice getting to this spot - it's basically in the center of the home.  The 'crawl' space is semi-enclosed but uninsulated (i.e. it will be around whatever the exterior temperature and humidity are).

This is in a very cold-weather climate (minimum temperature around -15ºF).

[PlainsWalker]

Every paper faced piece of insulation I've worked with included in the instructions that it needed to be covered with drywall. If I recall correctly the concern is flame spread. This PDF had a fairly solid rundown: http://paragoninspects.com/articles/pdfs/insulation/paper-facing-fire-hazards/insulation-exposed-face-reversed-vr.pdf

[nereo]

right - but as I understand it faced insulation in a crawl space would have the facing touching the floor/ceiling (in otherwords, 'pink-stuff' facing out).  In otherwords, it wouldn't be left 'exposed' as the PDF indicates...

[PlainsWalker]

Ahh, well in that case the question comes down to whether you want the vapor barrier or not. Since it's currently not insulated there is a lot of free air flow there. I'd be disinclined to introduce a possible moisture retention issue between the facing and floor by using faced insulation.

[robartsd]

I understand the facing provides a vapor barrier, but what I'm unsure about is whether I need one or not.

There is zero change of any rain, snow or ice getting to this spot - it's basically in the center of the home.  The 'crawl' space is semi-enclosed but uninsulated (i.e. it will be around whatever the exterior temperature and humidity are).

right - but as I understand it faced insulation in a crawl space would have the facing touching the floor/ceiling (in otherwords, 'pink-stuff' facing out).  In otherwords, it wouldn't be left 'exposed' as the PDF indicates...

The main purpose of a vapor barrier is to prevent moisture in the air on the warm side of the insulation from condensing within the insulation - the humidity on the cool side of the insulation is pretty much irrelevant. I imagine that your utility room is not very humid and the floor finish may already provide a vapor barrier. I'm with PlainsWalker in thinking that unfaced is more appropriate here.

[DoNorth]

agreed, it's not relevant with the configuration you're proposing.  With those kinds of temperatures you really do want to consider putting foam board around the exterior perimeter of your crawl space at some point.  Aren't your floors really cold?
 4" thick glued together would do the trick along with cutouts foamed into the rim joist.