The facing serves as a vapour barrier. So, in a heating climate, you install it face down.

However, faced batts may be unnecessary or counterproductive depending on: 1) what vapour control layers are already in place in the ceiling and 2) your climate zone.

You haven't posted your Zone, so open the link below for the recommendatons for your zone.

Here is a link that might be useful: Vapor Control Layer Recommendations

Why are you interested in mineral wool for insulation?

Foil faced insulations are a greater benefit in areas where sound reflection is needed.

Does the reflective facing really offer any more heat retaining/reflecting value?

no.
for reflective surface to reflect, it needs
a minimum of 3/4" or larger air space to work.
facing the reflective surface down..(as in vapor barrier
to warm side).. puts reflective surface on attic floor.
facing reflective side up..would work in hot climates
as a radiant barrier..but only until dust buildup
reduced reflectivity.

I used fiberglass batts in my attic. all
unfaced. first layer in joist bays, second layer
across joist bays.
just what I did in my own house.

before adding insulation, air sealing attic floor
to living space below is a good investment.
if you minimize air flow through insulation, it
will perform to its rated R-value.
caulking wire penetrations, plumbing penetrations,
sealing around vent fans for baths & stove vent
penetrations all help.

if your ductwork is in
the attic you should seal ductwork prior to any
added insulation.

it is much much easier to work in attic prior to
insulation. it will never be as easy again.

where are you located?
I'm interested in what you chose and why.
if you don't mind sharing.

for further reading on vapor barriers here
is a link to a blog that has some great info.
peruse some of the earlier postings also.

http://www.energyvanguard.com/blog-building-science-HERS-BPI/bid/54110/You-Don-t-Need-a-Vapor-Barrier-Probably

best of luck.

Sound energy would not be affected by a thin layer of aluminum foil but a sheet of lead is very effective against lower frequencies if it is hung lose in the wall cavity.

Thanks for all your responses. I think I am going to choose mineral wool for the following reasons:1 there are floor boards that do not fit tightly together, so the thought of blowing in cellulose into these spaces concerns me. It would be very dusty up there and the area is used to store old memories. Second, air sealing is so important, if I have to remove the boards to air seal, I might as well put down a product with the best R value I can find that will not compress over time losing its efficiency. Also I would never consider fiberglass for those reasons as well as the fact that it is soooo itchy to handle!!! The one thing I do not like is the weight of the packaged product. I am trying to think of the easiest way to get it up 3 flights of stairs to the attic. Any good ideas?

What about a rope and pulley system to hoist it up to the window?

The one time I personally installed Roxul rock wool I found it much more itchy and irritating than fg. (Not everyone has the same reaction.) The bundles are heavier than fg and don't compress. As well, it's not easy to cut; contractors regularly use table saws or specialized equipment.

I'd strongly suggest you work with a bundle before ordering any more. If you find it's not for you, it's not wasted money. Just put in what you have and finish the rest in another insulation.

assembly line.
line all your buds up from truck to
attic and pass bundles (or batts)
along into attic.

I had to haul batts through my
house & into attic via closet & tiny attic
hatch. it was more work than putting insulation
in place.

if you have a window the pulley & rope
isn't a bad idea.

best of luck.