Work on basement ceiling insulation with stone wool

10cm PUR (WLG 025, aluminum-coated) has 0.235 W/(m²K). Fleece-coated (WLG 028) would have 0.261.
14cm rock wool (WLG 040) has 0.266 W/(m²K).

May I ask again:
I can get a leftover Iko enertherm f4 (flat roof insulation) 100mm thick from an acquaintance.
Can I also use this for the basement ceiling and the upper floor ceiling?
Thank you!

Well, I'm not an expert, but I don't see why not. Maybe can add something to that?

May I ask something again:
I can get a leftover Iko enertherm f4 (flat roof insulation) 100mm thick from an acquaintance.
Can I also use it for the basement ceiling and the upper floor ceiling?
Thanks to you!

You can use any insulation material on the underside of a concrete basement ceiling. Vapor permeability does not matter since the concrete ceiling is practically 100% vapor-tight. UV stability does not matter, compressive strength and fire protection only in garages. Therefore: yes.
If it is aluminum foil faced, I would recommend doweling, otherwise the whole stuff might not hold.

You can use any insulation material on the underside of a concrete basement ceiling. The vapor permeability does not matter, as the concrete ceiling is virtually 100% vapor-tight. UV stability does not matter, compressive strength and fire protection only in garages. Therefore: yes. However, if it is aluminum foil laminated, I would recommend doweling, otherwise the whole thing might not hold.

okay, thanks. Is the WLG of about 022 the same for every PU/PIR insulation thickness? According to my research, I came to that conclusion, which would be unusual. Because the optimal would be max. 8cm and for gluing (so not double aluminum foil laminated)

is the WLG of approx. 022 the same for every PU/PIR insulation thickness? According to my research, I came to that conclusion, which would be unusual. Because ideally it would be max. 8cm and glued (so not double aluminum laminated)

The PIR without aluminum lamination has "only" WLS 025-027, since the aluminum as a radiation reflector is missing. When mounted on the ceiling and glued with PU insulation adhesive, of course the thermal bridges caused by the dowels are eliminated. From that perspective, at the end of the day it might not make much difference. The PIR with double-sided aluminum lamination is always specified with WLS022. Without lamination, the WLS decreases with increasing insulation thickness, so that in total it probably always results in 022. Why, I do not know.

The PIR without aluminum facing has "only" WLS 025-027, since the aluminum as a radiation reflector is missing. When mounted on the ceiling with bonding using PU insulation adhesive, the thermal bridges caused by the dowels are of course eliminated. From that perspective, at the end of the day, it probably doesn't make much difference. The PIR with aluminum facing on both sides is always specified with WLS022. Without facing, the WLS decreases with greater insulation thickness, so that overall it probably always comes out to 022. Why, I don't know.

Sorry to bother you, but can I omit the vapor barrier / seal when insulating the upper floor ceiling with the aluminum-faced variant?