Purchase or construction in Berlin / surrounding areas, realistic?

35 degrees on the terrace.

You have to consider that you will eventually have that inside the house too without countermeasures. And in a modern building unfortunately faster than you'd like. In Berlin, 2-3 days (up to a week) of a typical summer are enough and then you have a stagnant 28°C in the bedroom.

How is comfortable warmth defined?

Hmm, well, comfortable means everything around you is evenly warm and when you walk around the floor is simply not cold. Maybe these pictures help: ...Comfort of heating types. Underfloor heating is closest to the ideal heating:

Ah, the graphics actually help me. We are currently heating upwards, but up there we don't get any of the warmth.

Usually, the designers have a reason when they draw the kitchen layout, and it's the same here. If you enlarge the kitchen by adding an island, you will hardly have any space left for the dining table. I would only extend the leg of the L at the top of the plan. But I hardly see an island as feasible.

What speaks against moving the dining table closer to the wall? I think I need to model this in 3D for myself. It's always hard for me to imagine the space based on floor plans. At the moment, we don't have a dining table.

That is wonderful and also matches my experience - my wife and I are enough for each other. What we have as luxury is pure cream - delicious but unnecessary. The discrepancy between what we need and what we want is often very large and the ability to distinguish one from the other is often quite foggy. How could people live without a walk-in closet in the past? They couldn't, everyone died. :D

That must be roughly the experience I had at the model home yesterday. So many seats they had there at the dining table... I don't even know that many people I want to invite to my home. I am still waiting for the cost calculation...

I am currently sitting with my back against the radiator and working on the floor because I am cold...

Then you should afford a fireplace ;) By the way, we have ours on daily, at least every evening, sometimes during the day as well. For that, the base temperature in the house is only 19 to 20 degrees; when you are active and doing something, that is enough, but for sitting, it is too cold for us. With the fireplace, we then have 25 degrees in the living room (open with the kitchen), which is pleasant and costs little. But that is actually a matter of preference; for once or twice a year, I wouldn’t afford one either.

But I don’t want to do without underfloor heating. Even if unfortunately the floor is not always warm everywhere, I don’t want to miss the even warmth, and radiators would also bother me; you limit yourself quite a bit in room planning with them.

What we included right away were roller shutters, even though we said to ourselves that we didn’t necessarily need them. And also electrically operated right away. That’s hard to retrofit later if you want it after all.

We don’t need air conditioning either. We just leave the windows open and create a draft in the evening. But we also live in the countryside, and in this “summer” we didn’t have a single tropical night and exactly two nights over 20 degrees. Even in the city, those are only a few nights per year. But there too, you have to consider where you build and what kind of warmth needs you have.

To which wall? Top of the plan or left of the plan? I suppose you want to lower the table. Then you block the pathways from the entrance because the table is in the way. And still, it will be tight with the island. But drawing it yourself with the correct measurements is definitely a good idea :) Unfortunately, the plan only has square meter numbers, but a little should still be possible

How is pleasant warmth defined? Sorry that I have to ask such a silly question, the last time I was somewhere with underfloor heating was quite a while ago.

That is a very, very good question. The perception of temperature is quite individual. We love it when the power of the sun can be felt on the skin. For us, a warmth that can be felt on the body (radiant heat) is especially pleasant. Especially in winter, we really missed that (and light) in our terraced house with underfloor heating. Therefore, we chose the heating system exactly according to the question of how pleasant warmth is defined for us. We heat with a masonry heater and the areas it doesn’t reach with a few infrared panels. Just assume what works for you, there are plenty of functioning systems.

To which wall? Top of the plan or left side of the plan?
I suppose you want to move the table down. Then you will block the paths from the entrance because the table is in the way. And still, it will be tight with the island.

But drawing it yourself with the correct measurements is definitely useful :) Unfortunately, the plan only shows square meter numbers, but a little should still be possible.

I would roughly estimate based on the width of the doors and windows and enter it into the Ikea kitchen planner.

I quickly put together in Paint what I meant and how I understood your idea. You are right, one of the doors would then be blocked. That is obviously disadvantageous if you want to eat in the garden in summer. (Or the table goes outside completely in summer because you eat outside anyway...)
Left is original, middle my first idea, right how I understood your idea? Red would then be additional kitchen area.
Otherwise, a narrower table would have to be used, or the kitchen would have to extend into the room, or maybe some kind of bar where you can sit?
It can hardly be that you can't make anything out of such a huge room.

That is a very, very good question. The perception of temperature is quite individual. We love it when the power of the sun can be felt on the skin. For us, a warmth that you can feel on your body (radiant heat) is particularly pleasant. Especially in winter, we really missed that (and light) in our terraced house with underfloor heating. That’s why we chose the heating system exactly based on the question of how pleasant warmth is defined for us. We heat with a masonry stove and the places it doesn’t reach with a few infrared panels. Just start from yourself, there are plenty of functioning systems.

I think that applies to most people; nothing beats the sun. Since money plays the overriding role for us, we have to stay realistic.