Insulate concrete ceiling upper floor

You need an energy consultant for that anyway. At least that's what ubakus roughly says. So it should be fine.

And is it a problem if the panels don't have tongue and groove?

No. Take aluminum tape and seal the joints.

I can't contribute anything on the topic of funding.

I just spoke with the energy consultant. He said that the material for insulating the top floor ceiling is NOT eligible for funding if done as a DIY project. I have now looked up the passage in the information sheet myself:

Bei separatem Kauf des Materials können die Kosten angesetzt werden, wenn die Anbringung beziehungsweise der Einbau durch ein Fachunternehmen erfolgt oder die fachgerechte Durchführung der Maßnahme und die hierfür angefallenen Materialkosten formlos zusätzlich zu den Angaben in der "Bestätigung nach Durchführung "durch einen Energieeffizienz-Experten gemäß Programmmerkblatt bestätigt werden.

Additionally, he said that the panels should only be glued from above with diffusion-open tape, otherwise moisture can penetrate into the concrete.

Best regards

The proper execution of the measure and the material costs incurred for this must be additionally confirmed informally to the information in the "confirmation after execution" by an energy efficiency expert according to the program leaflet.

This applies to all in-house work. Where is the energy consultant's problem with providing the confirmation? I have never had any problems with that before. That’s what you pay him for.

Just call the next energy consultant. The KfW also has a free hotline. Why would anyone want to tape something there, especially not on the outside. The building materials dealer has given absolute nonsense.

Well, I have already submitted application 430 (for windows) with this energy consultant. But I have now sent him an email asking if he would confirm the proper installation for me. However, I would then have to have the application changed. That means I could also just lay the insulation material without gluing it, right? Then the moisture can escape better. Regards

The vapor barrier is on the inside, and protection against driving rain is hardly needed with a tight roof. Apart from the concrete ceiling. But that is the task of the energy consultant colleague; he must also demonstrate moisture protection in connection with the insulation.