Away from fossil fuels - House from 1999

He was already old back then, now he has been dead for a long time.

He surely had radiators and now he is dead...

That mostly came back then from the only civil engineer in the family circle, who always had an opinion on everything,

Oh yes, like my late "Aunt Analysis" - she (and other directors' widows from her charity circle) also always knew every nonsense exactly :)

Does anyone have any idea how to best find a really clever independent consultant in Berlin who looks at it with an open mind?

Doesn't have the best overview of the intellectuals in the Berlin heating scene here?

We faced a similar question, (geothermal) heat pump or pellet heating system, and decided on the pellet heating system (Easyfire from KWB).

Our house is from 1983, living area 265m2 plus 130m2 heated basement. Heating oil consumption before renovation to KFW 100EE around 3500-4000L per year, which I already found not bad for the age and size. The oil heating system is from 2015.

Ultimately, the decisive factor was the price. The geothermal heat pump including 4 drillings would have cost 65,000EUR before 50% subsidy (replacement of oil heating in the individual renovation roadmap). The pellet system (including hot water circulation, which the heating installer is still doing) is at 44,000EUR, with 55% subsidy.

Would a pellet system be an idea? Often you can recycle the room from the old tank.

Do you still remember the presumably very interesting explanation?

I had read it too (long ago):

this narrative claimed that people with varicose vein problems have to expect their issues to worsen due to overheating from below.

Perhaps if you mostly walk barefoot on the ground, there might be an effect in my opinion. But who does that anyway?
Besides, the temperature of the ground is usually below 30°, and there the influencing effect should be practically ZERO.

Personally, I would not consider pellets. The CO2 from burning wood is just as harmful to the climate as that from fossil sources. And no - it does not grow back as easily as our bark beetle-infested forests impressively demonstrate. Then these things still have to be produced and transported with a great deal of energy. High maintenance costs, fine dust problems, and exploitation are added on top. Regarding expensive ground probes: that does not have to be anymore. Air-to-water heat pumps have improved a lot in recent years. With R290 as a refrigerant, a lot has happened, especially at higher flow temperatures. An alternative for very cold regions might possibly still be the trench collector.

It was just done that way back then, but if the solution today looks like replacing the radiators with 33mm ones, then that is an acceptable effort. Does anyone have an idea how to best find a really clever independent consultant in Berlin who looks at this with an open mind?

Well, that's just how it is now. Complaining about the reasons back then doesn't help anymore. Focus on the low-temperature radiators or keep the existing ones and look into pellets. But it's not cheap and only half sustainable.

Do you still remember the probably very interesting explanation?

Underfloor heating with high flow temperatures is considered unfavorable because this leads to water retention/oedemas.
But madam will be pleased at first.
We have already read plenty of feedback here about underfloor heating because the feet are not glowing as expected after all.