Classification of new construction

We did not insulate at all (or only the base plate) and have a Kfw70 house. However, we also have a 36.5 cm wall.

I am fairly sure that you have also insulated your roof. Insulation is more of a material property after all – if you install 36.5 cm of material with a U-value of 0.09 W/mK, that is also insulation. You can quite easily calculate what insulation brings... the difference between a U-value of the exterior wall of, for example, 0.15 W/m²K and 0.24 W/m²K would amount to about €100 per year in heating costs (1400 kWh) for our house. Costs for the insulation: one layer of mineral wool at 8 cm for 200 m² of exterior wall. Material price €1200. Additional effort, due to another layer, about another €1000. Not a great return, but also not a losing investment.

hahaha, true, the roof is of course also insulated and the floor slab ;-) I was assuming an additional insulation of a wall. And uninsulated means to me, just without Styrofoam or something similar that's "smeared" on the outside of the wall. It's also clear that a stone insulates or can insulate if the right one is used. And yes, we installed the 0.09 W/mK ;-) By the way, we also decided against ventilation and exhaust.

I was just about to say that. Nowadays, building without insulation? Or not using materials with good k values? Then you only have yourself to blame if money seeps through the walls. On the topic of over-insulating. In my eyes, the house must form a complete picture of insulation and heating system that is tailored to the occupant. It’s absolutely pointless to stuff your house with an additional 100mm of insulation if I have a 20 kW stove in a 15 sqm living room. Always consider the overall picture. Even prefabricated houses today have such a high insulation standard.