We purchased our first home last spring and the home inspector highly
recommended we further insulate the attic before the winter season. The
house was built in 1958 and is located in Ottawa, Canada where it does
get quite cold during the winter months. Right now we have about 6
inches of blown in fiberglass (White in color but has the texture of
fiberglass) that fills the ceiling joist cavities. I am unsure what the
exact R-value of this type of insulation would be but I would assume it
would be approximately R-20.

1) What R-Value should I be aiming for?
2) I was thinking of installing rockwool bat insulation perpendicular
to the ceiling joists on top of the old stuff. I was wondering if I
should just remove all the old stuff and re-insulate with new material.
3) It looks like a wax paper type vapor barrier was installed. How
effective would this type of vapor barrier be? I am assuming that
barrier along with the several coats of alkyd paints that were applied
to the ceiling over the year should be sufficient?

Any advice would be much appreciated,