Roof insulation polyurethane PU rigid foam 100mm thick

It always makes sense to familiarize yourself with the subject matter. You can see it negatively or as a challenge. The architect can look at the conditions on site, especially in old buildings this is useful and the money is not badly invested if in doubt. An engaged and experienced craftsman can of course do this as well.

When I inquire about a new roof and thermal insulation, the roofer gives proper advice. If I inquire about a new roof, thermal insulation with thermal protection and good sound insulation, then his advice is completely off. What was he specifically asked?

You may be right.

However, I personally have a completely different idea of service. When I hear "expert," I assume that he knows about the entire field.
I don't let a customer walk into ruin just because he only wanted "warm" in winter and never mentioned "cool in summer."

But that's just how it is in DE. There's nothing you can do about it. The term "service desert DE" didn't come about for no reason. And what "Made in Germany" is worth, we have known since the Diesel scandal at the latest...

: Thanks for the detailed explanation

I see it less negatively, also because I often have good experiences. But in my opinion, it is more effective to seek advice for such matters from companies that combine roofer-plumber-carpenter in one house, thus mastering the entire component "roof." The advice is then, let's say, more comprehensive and not so narrow-focused on my trade/my invoicing. K.

Hello everyone,
Thanks to all who are participating I think that’s super cool of you.
We will have our roof done, yes... it was important to us that it is well insulated. That’s why PU boards were recommended to us.
My search on the internet showed that these boards are good but not so good when it comes to thermal and sound insulation!!!
That’s why I kept searching and reading. Now my opinion is that WOOD FIBER BOARDS are also better due to their mass in terms of sound and heat protection. Thermal insulation especially. Additionally, we plan to do an insulation between the rafters... because of these phase shifts. We haven’t contacted an architect so far.
I think he can’t really suggest much more (or something completely new) to us. There are just these “on-rafter”, “under-rafter” and “between-rafter” insulations... with different materials. I think the wood fiber boards are definitely better.
Get into the topic. You have to read a lot. I have even understood this U-value calculator by now

Have you looked around the KfW site in the meantime? Can you get a grant?