Mineral wool density grade

[svouts]

I am sound insulating the ceiling between the joists with mineral wool. I am thinking to use either 45k/m3 or 60k/m3 density mineral wool. The joists are set 30cm apart so I will have to cut to size the mineral wool to fit between the joists. What density will be easier to:
1. Cut to size?
2. Fit tightly between the joists?

 

[JohnD]

if the purpose of fitting it is to improve sound insulation, then the heaviest batts will perform better, and will pack into the gap better, so they are the right ones to use.

I don't think they will noticably be more difficult to cut.