Roof insulation Styrofoam or Isover

Just a quick question: I intend to retrofit insulation on the inside of my roof in the uninsulated area. I could use mineral wool (Isover) or Styrofoam. Which is more sensible? And how do the application thicknesses compare? I mean, what is the thickness ratio for the same insulation value? Isover is 16cm thick (0.032W). How thick do I need to make the Styrofoam to achieve the same value? I think Styrofoam is easier to work with? Thanks in advance.............................................

I intend to insulate my roof from the inside afterwards in the uninsulated area.

Roof or top floor ceiling? Purpose of the insulation? Attic conversion?

I could use rock wool (Isover) or polystyrene. Which is more sensible? And how do the application thicknesses compare. I mean, what is the thickness ratio for the same insulation value. Isover is 16 cm thick (0.032 W) How thick do I have to make polystyrene to achieve the same value. I think polystyrene is easier to work with?

Check out ubakus on Gurgel. There you can calculate everything yourself. Otherwise, the question remains whether you have any knowledge about the correct construction of insulation? By the way, mineral wool is much easier to work with. And there are other insulation materials that, for example, have significantly better insulation performance. It all depends on your very specific requirements. See my first question.

Thank you for asking.
Roof - not ceiling. House with a gabled roof is developed at the top. Upper floor to attic is insulated.
The attic to the roof is only boarded, then roofing felt, then slate covering.
Inside, I still have space between the rafters to add additional insulation.
It worked well for years, now due to the new energy discussion I thought if I additionally insulate the attic, which is currently not insulated on the outside, it might still bring some benefits.
I was already at the hardware store today. Styrofoam is more expensive with similar insulation value. It also burns.
So I will take mineral wool, which can also be cut well.
Thanks for the tip (mineral wool), I thought that was only for facades. It is probably more dimensionally stable, so it fits well between the rafters.
I will research price and insulation value.
As mentioned above, for years one hardly thought about it, now due to the price situation one starts to recalculate.
My oil cost 0.75 last year, this year 1.52.---- You really grit your teeth.
My wish for everyone: Hopefully the price for gas will also go down again. (But I hardly believe that..........................)

OG to the attic is insulated.

If you don't need the attic otherwise, just lay mineral wool in two layers on the floor and that's it. That would be an alternative.

Thanks for the tip, but I use the floor as a storage room, so the mineral wool will probably get damaged there. The space between the rafters is available, which is why I think I can better fit the additional insulation there. Mineral wool is by the way more expensive according to my research. Ok for the facade, but with rafter insulation, precision and fit are not that important. As part of the insulation considerations, I had also thought about the facade, but after recalculating and the amortization calculations, I’d rather burn my money in Bermuda. Also, when reading through the discussions here in the forum, I notice that with a (also industry-promoted!) hype, exact recalculations get lost. The important thing is that new investments are made, no matter how the calculations turn out. Some people think they are participating and saving the environment and do not inform themselves about what is happening in the rest of the world. From a human perspective, that’s very positive - but? With best wishes for more sun on the roofs of our photovoltaic and heat pump experts.

I insulated my rafter space with Styrofoam. I am very satisfied with it.

This is because I absolutely hate mineral wool. I cannot tolerate those flaky little hairs and the itching.
Therefore, I did not use it for that purpose. I only used it for the ceiling between floors, but there it lies between the ceiling without contact.

However, I did not use hardware store Styrofoam, but special Styrofoam for the rafter space from Schwenk. It was slotted, so it could be bent slightly and thus fitted very precisely. With tongue and groove. So it was very easy and quick to work with. I installed a total of 15 cm + drywall. Even in the height of summer it remains comfortable in the upper floor. And nice and warm in winter. So I can only recommend it.