Chris Bacon wrote:

Rockwool is slightly less irritating.

It is also a little duller and softer. Fiberglass is usually quite a
bright yellow. Both are irritants though. Fiber glass is awful. Throw
your clothes away when using that. And wash you hand before you go we
wees, not just after.

Make sure you have no draughts through from the loft. A cold bath will
wash the glass away. But you will have to wash your clothes three or
four times.

It depends on who told you it was rockwool/fibreglass whether the
people who laid it are at fault. For the general everyday use the terms
rockwool and fibreglass are interchangeable.

If someone not directly involved in the contract has used the term
loosely, all they have to do is deny they said it.

It should make a tremendous difference whichever they put down, come
next winter.