Construction costs are currently skyrocketing

I say from experience that this is nonsense.

I say from experience that this is not nonsense.

Can you please explain or provide a source? Thanks.

Probes are designed for a specific withdrawal capacity, there are formulas for that (google). The drilling person does that for you. If probes are overloaded, they (or more precisely their surroundings) can freeze, which is either irreparable or requires a considerable amount of time to regenerate.

Sources are forbidden here.

Since Monday, I have been heating with Hotboy. I can give you an update tomorrow on what has been running until then. The drilling has been there since May, but it is not allowed to be used because of the risk of freezing. As far as I know, the heat pump is also not there yet ;)
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Our heat pump has long been there but is stored at the heating technician's warehouse and will only be installed once the flooring is laid. Since the screed heating would run anyway over the heating rod and not via the probe, it makes little sense to install the heat pump now; the Hotboy works just as well.

Regarding screed prices: €13/m² for 100 mm insulation fully laid, screed heating 60 mm for €16/m², each net.

they receive compensation from cyz amounting to at least two-thirds of the market value.

It’s right there. Of course, you can sell or inherit it during the term. But if the contract expires and is not renewed, you get two-thirds. The lessor will certainly not do the devil and pay you more than the minimum. And with that, the lessor has you in their hand. If you as the owner do not agree to the new price, you simply lose one-third of the value. That quickly puts us in the range of 100-150k. And if you sell the house now, every reasonable buyer will also take that into account when determining the price. Especially with not very long remaining terms. That makes your house lose value compared to a house that belongs to the property.

So my grandfather built on a leasehold property of the church in 1966 with a term of 99 years because at that time he simply couldn't have afforded it any other way. A few years ago (don't remember exactly when) he then bought the property. I just want to say that the leasehold doesn't have to be permanent and that you might eventually have the opportunity to buy the property later. That way he was able to pass it on as a family-owned complete package.

The cases exist, but one should be realistic. Only the 99 years are guaranteed, and one should not commit to a leasehold just because there is a vague hope of being able to buy the property after half the term.

There are such cases, but one should be realistic. Only the 99 years are certain, and one should not get involved in a leasehold just because one has the vague hope of being able to buy the property after half the term.

It also depends very much on who the leaseholder is. In times of poor municipal budgets, there have occasionally been sales, but with church foundations or the like, there is often no chance.