Rockwool does slightly less than **** all for sound insulation, and in
walls, it tends to fall down, which is why its not recommended for thermal
much either.


With respect, that is ********. Acoustic insulation in plasterboard
partitions is either rock fibre, or more normally, glass fibre. The normal
product used is Acoustic Partition Roll (APR) that is a high density glass
matt.

Rock fibre can be used as well, due to it's higher densities.

As to cavities, correctly installed glass or rock will do the job, and will
not sag or slump over time.

Boards are fine, but if there are *any* gaps the insulation is useless.


SalesGuy