Construction costs are currently skyrocketing

And the entrepreneurs don’t know that and don’t raise prices by this factor ^^

Well, always these evil entrepreneurs! Get involved politically at last, change Germany in your desired direction, but don’t keep whining or scolding those who take what they can (because the current political and social system allows it). I really can’t listen to it anymore... Or alternatively become an entrepreneur yourself and make use of the system. But feeling comfortable in the victim role? That can’t be it – can it?

I don't renovate ;) so I don't really care what rules are set here... I just see the risk, especially for older or low-income families, of losing the house...

I don’t renovate ;) so I really don’t care what rules are set here... I only see the danger, especially for older or low-income families, of losing the house...

I also don’t think a requirement upon possession is good, but renovating to a KfW standard when selling wouldn’t be wrong at all. I have a case in my colleague circle. Huge house 340m2 living space from the 70s bought cheaply in 2012 and now he’s wondering about the heating costs. If he had done the facade back then and got rid of the oil heating, he could be happy now, but now he has to do it even though it’s currently inhabited.

For me, insulation is, for example, purely a mathematical calculation (perhaps also for colleagues?). You can calculate when the investment has paid off due to lower consumption with presumably rising prices (I take the median of the last 10 years to exclude the peaks), including the gain in living comfort. Everyone must evaluate this for themselves. Furthermore, replacing the heating system and applying external insulation in an occupied state is unproblematic.

On the subject of insulation:

Of course, it was considered, but is it really sensible? Do you really want to spend that much money to completely insulate a house that has now become too large and replace the heating? Put 20cm of insulation on 60s rubble stone walls? The rooms back then were comparatively "small" with low ceilings? And so on... To make a long story short, I think everything will stay as it is and in 10-20 years the house will have reached the end of its useful life and will be demolished. Whether by the current owners or others is another matter. Personally, I find it hard to imagine that anyone would invest a lot of money under such conditions; it is also an investment for the next 40 years, and the space, building style, room sizes, etc. simply do not fit with the way we build/live today and in the future.

Just a stupid question, what kind of house is this? Depending on the type of wood, that's 60,000-80,000 kWh of calorific value! Is it really that inefficient or is it an uninsulated barn?!?

Old building, 280 m² living space with 3.10 m ceiling height, so from the surface rather 300 m².
The house has 6 cm internal insulation, new windows from 2006 (Uw 1.1), 12 cm floor ceiling insulation. The floor still has potential.
So far it's 30 RM per year, but the rooms are to be expanded, and in return we will eliminate a few weak points: upgrade the old entrance door, insulate the wall to the unheated area (Tenne), double the floor ceiling insulation) maybe the demand won't increase, but it will probably be 30 RM.