Roof insulation polyurethane PU rigid foam 100mm thick

Yes, thanks for the tips Nordlys... Our attic is going to be inhabited after the work on the roof. That is why thermal insulation and soundproofing are so important. Are there other users here who have more experience with the topic of roof insulation???

Have you ever talked to an architect or similar about what is possible and sensible for you? Is everything new including interior finishing, so can you also access it from the inside?

I see no reason why you should give up cheap insulation between the rafters, or what is planned there? If that is not enough, as an additional measure, insulation above the rafters is typically applied when the roof is re-covered. Material with high density, such as wood fiber, is better suited as protection against heat.

Only 10cm of insulation in total will provide little protection against heat. I would also avoid expensive 023 insulation, it is only used when there is really little build-up height available.

Hello Boxandroof.... Thanks in advance. No, we have not contacted architects or similar. Only roofer craftsmen... including offers. The plan is: 1. To reroof the roof. That’s why we were told that it makes sense to install an puren Protect N 023 rigid insulation above the rafters. 2. Insulation against cold and heat / The attic should be used as living space. 3. We were told that if you install insulation above the rafters, you no longer need insulation between the rafters. That's why we wanted to remove the "old" insulation from the inside and cover it with drywall panels. So should you rather use wood fiber boards when installing insulation above the rafters??? Or rather do without insulation above the rafters and work with insulation between the rafters???

There are many possibilities. I would advise you to look at and plan everything with an architect. If the roof is to be inhabited all the way up to the peak, then good heat protection makes sense; as you are doing it, this is not the case.

Insulation between the rafters: it depends on how much build-up height fits between the rafters, do you know that? That can be enough against cold - but heat protection is then not great. In new buildings, 20cm of 035 mineral wool insulation between the rafters is inexpensive and the minimum; in old buildings, possibly less fits.

It gets better with additional insulation above the rafters. Against heat, you can also apply material with high density on the inside (no plasterboard).

I did the rafter insulation according to the Energy Saving Ordinance five years ago with PUR and an allegedly special insulation material that has a mineral wool facing of several centimeters. Overall, I have a U-value of 0.14. I can't tell you the exact thickness. But it's definitely about 20 cm. One thing I can say: the heat protection is miserable, as is the sound insulation. I am annoyed that neither the energy consultant, the architect, nor the roofer pointed out the wood fiber insulation materials given the airplanes circulating above us. Due to their high bulk density, they provide better protection against heat and sound. However, they are somewhat worse for cold protection, meaning you need more build-up height. Nowadays, the following is done: a combination of insulation between the rafters (you can't use that space anyway) and rafter insulation. Most roofers won't suggest this to you because it's easier to simply lay a layer of PUR boards on the outside of the rafters and nowadays work with unqualified helpers because it's cheap. But that doesn't help you. If you want security, check a fictitious roof build-up in a U-value calculator on the internet, whose link I am not allowed to post... (but you can google Ubakus) - but pay attention to the values for phase shift. It should be more than 10 hours. This indicates the time it takes for the heat to penetrate the building material... Everyone only looks at the cold protection. That is excellent in our roof too! But in summer, after three hours of sun, it is unbearable. Not to mention three days of sun... Inform yourself on the websites of the companies Steico, Gutex, or Pavatex about the material. It is also ecologically more sustainable and you do not produce hazardous waste. So I give you a clear vote for wood fiber insulation materials... these are, of course, somewhat more expensive than the common Styrofoam. But those who save sometimes build twice... I am now installing an air conditioning unit and additionally insulating between the rafters with Steicoflex mats, a counter batten, and Steico universal boards instead of drywall.

I also have a PUR insulation with a mineral wool layer (about 5cm or so). I find the heat protection good, it only gets warm in the apartment after days but rarely above 26 degrees. I think you don't get much further with wood fiber. It simply heats up in the height of summer, you can't do much about it.

The sound insulation is correct, it is not particularly good. But it probably also depends on the angle. Under my dormers it is louder than under the slope. By loud I mean you can hear some low-flying planes, but under the slope it is not like that.
If sound insulation is important to you, then better do something else like rigid foam.