Base plate with concrete core activation. What is your opinion?

I am just pointing it out, then the OP can take the topic to his planner.

By the way, I was not successful in finding any entry anywhere where something like this was ever done.
I would not try to save money in the wrong place here.

The supply temperature must be calculated specifically. However, low supply temperatures are obviously also no problem in the screed. Additionally, placing it in the intermediate ceiling would also be an option. You have simply unlocked even more storage mass with the Swedish panel. And hopefully a top U-value. I haven’t looked it up yet.

According to statements, the Sweden slab does not need impact sound insulation,

I consider that to be advertising nonsense.

Leakage test.

Oh, I see. But I think the OP is more afraid of sharp stones in the concrete.

The Sweden slab basically only works with a timber frame house.

I first read the term (not specifically the Sweden slab, but concrete core activation) several years before residential construction in commercial construction. That is, where reinforced concrete skeleton construction is still widespread – even if, apart from the firewalls, most walls are lightweight and the facade often hangs in front of it.

Is it more a hint that one has to be prepared to do some sanding, or is it really a bigger problem when it occurs.

You will rather smooth concrete by filling it up than by grinding it off. I would not omit the screed. Also because of the impact sound: it does not only affect the rooms below, but also adjacent ones – and it is advisable that the covering can float.

By the way, a moderator will probably complain soon that external links should not be here.

Just browsed a bit and skimmed through the website. The slab is probably leveled using a laser, which should then achieve a ready-to-cover surface. The stones in the concrete... well, no idea. It’s their business and they must know what they’re doing. I also have to admit that the impact sound insulation doesn’t make sense to me. Experienced builders would really be needed there. By the way, I saw that they only use 10cm of concrete. So they don’t have as much thermal mass as expected. But they do have a U-value of 0.17. That’s really good.

The tip about JACKODUR was pretty good. I looked into it and then came across the Thermobodenplatte from IfU (Institut für Umweltenergie). Just search on Google for "thermobodenplatte ifu". It should be the sixth result. Very short domain name.

I had a few nice phone calls and so far I am very convinced. Actually, I was only looking for comparable U-values, but they couldn’t give me those. JACKODUR only provides the thermal conductivity and the exact U-value has to be calculated. Since Jackodur is certified for passive houses, this value should be very low in any case. On the website, there is a notice from >012.
The costs roughly estimated were also reasonable, since you mostly get the materials directly from the manufacturer and you only pay for the labor if you need it. For example, 40€/m² for the JACKODUR, about 15€/m² for glass foam granulate, 25€/m² for the heating, etc.

I also find it interesting that, for example, it is not compliant to use two different rigid foam boards. Now I wonder how the Schwedenplatte handles this, since it uses EPS and XPS. I then took a closer look at theirs and the EPS boards are not placed where the walls will later stand. Interesting...

I also found the information about concrete as an energy storage medium interesting, and that based on a project, it was found that in winter it was sufficient to activate the heating only every few days (e.g., when the sun shines). Due to the insulation and the concrete, the temperature inside remained constant. Of course, you don’t know all the details now, but you get the figures on how much energy concrete can store. For the upper floor, however, you should stick to classic screed and underfloor heating. This is mainly because of impact sound insulation. In the ground floor, impact sound is not a problem. An additional luxury would also be a concrete ceiling, which can additionally cool in summer. But it is not necessary.

I just wanted to share the info here with the group. Not everything may be fully questioned yet, but so far it looks promising, serious, and of good quality.

That is XPS, presumably WLG 035. You can enter it into any U-value calculator. The desired U-value of 0.17 is achieved with 20cm material thickness.

I wouldn’t tinker with the foundation myself. The principle, the construction method is now known. Basically, anyone can replicate it. Lay out XPS, put formwork on top (that’s peanuts) and produce the slab as usual. The lateral perimeter insulation is either integrated directly or applied afterwards. You don’t need a kit from Jackodur for that.

But as I said, whether like this or with EPS under the screed, purely in terms of insulation, it delivers the same. I would choose the cheaper option. Especially since with screed and KS walls there is already plenty of thermal mass in the house.

What you mean by mixing EPS and XPS, I didn’t understand.

Is a slab foundation even (economically) possible on your plot?