ᐅ Wall thickness? Facing brick / insulation? Cavity wall with 3D steel tie system / render

I’m new to the house-building forum and wanted to say hello here!

Now to my issue: in about 2-4 years, my future wife and I want to build a house (solid construction). We’ve already chosen a model from a prefabricated house supplier, but we want to replicate it ourselves since it would only be affordable with our own labor. I’ve been working on a rough cost calculation for the past 1-2 weeks and need help with insulation.

The exterior wall of the house is planned to be made of facing bricks/clinker bricks measuring 240*115*71 mm (9.4*4.5*2.8 inches) NF size, followed by insulation — which is where I have no knowledge (this is my problem) — and the interior wall is planned as a solid block (KSS) 240*175*113 mm (9.4*6.9*4.4 inches) 3 DF, laid lengthwise to reach a thickness of 240 mm (9.4 inches), finished with plaster, which I think is about 15 mm (0.6 inches) thick unless I’m mistaken. Without the insulation, the wall thickness would be approximately 370 mm (14.6 inches) so far.

If someone could also provide a suitable price per square meter for their suggested solution, that would be perfect, but it’s not a must. If I know what to look for, I can figure it out myself.

Like most people, we want to save energy costs (around 280 m² (3,014 ft²)) and would like a house with a U-value matching a KfW 60 standard, preferably even as low as KfW 40. Of course, standards could change in 2-4 years and these requirements might no longer be sufficient, but they are good enough for initial calculations. It’s also about qualifying for subsidies and so on.

I have already tried using a U-value calculator, but I struggled with selecting the right parameters to enter there.

I would appreciate any help or suggestions in this regard.
Best regards, doberman123