Convert paved extension into living space

Thank you! Well, actually the living room was planned there and I like it nice and cozy warm... Problem, I know! But where do I start now?

The budget for that is also rather tight...

Then I would quickly discard the idea of the living room.

But I’m overheating myself to death, just the way it is now.

Close the door to the covered terrace again and live only inside the house. Otherwise: excavate the floor and build an insulated floor slab (whether concrete or a wooden construction). But that only solves a small part of the problem. The walls and therefore mainly the windows are energy wasters. The roof will be as well. To serve as a living room and not overheat yourself to death, EVERYTHING should be redone.

How high were the heating costs in the past? Show me the floor plans. Maybe it is possible to live in the house without major renovations. The previous owner was able to do that as well.

I have attached the floor plan. Where it says Wintergarten and Flur, everything is paved. I have received no information about heating costs. The house is from 1960, the extension/Wintergarten from the 90s. It is heated with a 30-year-old gas boiler. Of course, one could simply separate it and use it only in the summer, but that's not really what I want. Couldn't the stones be removed and covered with insulation boards?

Couldn’t you remove the stones and cover it with insulation boards?

And then? a) It’s a great and cozy floor and b) what do you do about the exterior walls and the roof? That will insulate just as "well" as your current floor. Do it properly and invest money. Everything else will just be botched.

Couldn't you remove the stones and cover with insulation boards?

The problem is physics. Heat will be lost everywhere – mostly through walls and ceiling. Only looking at the floor would be like wearing a T-shirt with thickly lined boots in winter. You can do it, but you will still be cold. (Conversely: thick winter clothes and sandals also don't make sense; apart from a few toes threatened with frostbite, the heat loss will probably be less.) It first needs to be clear how much heat is lost through walls, windows, and ceiling. I fear the floor is the least of the problems here. I would consult a professional first to get clarity.

Interesting floor plan. From the kitchen through the conservatory, through the bathroom into the living room? Who designs something like this?