there is anything instead of CELOTEX?

Hi, I can't find Celotex in my city, and I want to know if there is anything wich can substitute this material for studio windows construction. thanks

semi rigid firbreglass cloth covered. Just to make sure this is for the inulation strips between the 2 panes of glass correct???? Celotex is stiffer than the semi rigid so it wont sag, but if you bolster the semi rigid (attach to the underside) some polystyrene then wrap with cloth, I think you will be ok.

thanks Giles, But 40kg/m3 density is ok? or 70kg/m3 is better? How can I attach the rockwool to the upper side of the window?

40..You are merely calming down reflections between the 2 panes of glass.