Construction costs are currently skyrocketing

That's so typical for the NEW BUILD Forum. Here, the top 10% loudly claim that one shouldn’t make such a fuss about the planned mandatory EU renovations. That’s what those in new build houses say. Of course. They themselves are not affected. No one could have predicted two or three years ago that gas prices would double, nor that the government's renovation plans would interfere so deeply with property. If you now have to renovate your 70s house for €70,000 in addition to the doubled energy prices, I can understand the desperation. That was not foreseeable at all.

I strongly disagree. Anyone not living under a rock and involved with real estate knew that. And that should be the case for everyone acquiring a property. It was foreseeable that energy renovations would be necessary. For buyers as well as owners. I have no sympathy for people who calculate the renovation nicely when buying a house and drive prices up, ideally combined with a 10-year fixed interest period, nor for owners. For those who were already owners and couldn’t foresee the increase, that goes back at least 10-15 years. With €3/sqm maintenance reserve to be set aside, that adds up to €81,000 in reserves over 15 years. This rule of thumb is no secret and would cover the necessary renovation. The reality is: people prefer to buy an expensive car or go on vacation and think they can run their house down for 50 years without renovation. It turns out: wrong thought.

Stay calm. Interest rates will be significantly cheaper again in 2024. It might even start at the end of 2023. Then the game starts all over again.

Inflation at 6.1 percent (May 2023) is still far too high to lower the key interest rate.
The fact that mortgage rates have recently declined somewhat also has the background that many banks are currently foregoing interest margin so that loan demand does not come to a complete standstill. If the key interest rate is lowered again, immediate passing on to customers is not yet to be expected.

It was foreseeable that one must renovate energetically. For buyers as well as for owners.

Yes and no. In the scope that is supposed to come according to the EU building directive, this was certainly not foreseeable. That you have to expect investments with an old house with poor energy efficiency, okay, but the decision power over the "when" and "how" was still with the owner. By now, there is a hail of legal deadlines and regulations, and the homeowner is basically just a recipient of orders who has to implement all that obediently.
In recent years, politics has repeatedly tried like a broken record to talk people out of energetically better new construction on a greenfield site and instead make grandma’s little house appealing. They wanted people to buy and spruce up these old huts. But with such old "treasures," it is clear that money is also needed for cosmetic measures. Everyone here roughly knows what two new bathrooms without frills can quickly cost. If I then have to renovate energetically almost at the same time because both energy prices and legal requirements overwhelm me, I may as well build new. I don’t think that buyers of existing properties in 2020/2021 had to have the further development already on their radar.

You just have to artificially (by the state) restrict new development areas, and then super prices will be paid for these houses again because demolition and new construction can/may also take place there

I didn't say that.

Yes, it was clear in 2020 that energy costs would politically be forced to rise sharply in the coming years.
[..]
That's why we factored in upwards of 100k for a renovation. With the effect that you actually didn't need to place a bid anymore, because the houses were then far too expensive. For the purchase price plus ancillary purchase costs plus partial renovation, I could build new in a similar location, including land, kitchen, outdoor facilities, and have a standard that clearly surpasses the renovated house.

It was exactly the same for me. From the beginning, I looked at how to bring an older renovation house up to the present. For that, you obviously need more than just a bit of paint and maybe a new window, and the price of the renovation basis must not be too high. Now the market has adopted this view and priced in the defects. That's where a quick €200,000 bubble surcharge is taken out of the property, and it still has to be energetically renovated.

Quite a dilemma now for someone who can manage neither the value correction nor the renovation. But also pretty much self-inflicted.

There is currently an agency report going through the media about living space per capita. Here is the graphic. It is very clear that at least a larger part of the average living space per capita is likely due to the increasing proportion of single households, especially older singles.

Which was clear to anyone with some insight into demographics and the housing market. But media and politics wanted to fuel a narrative about land consumption and space-hungry residents who simply do not want to recognize the advantages of a Berlin rental barracks from the (pre-)last turn of the century. Thus, the “evil” families with 2-3 children in the even more “evil” single-family house or semi-detached house have often been associated with 50m² per capita..

You just have to artificially (state) restrict new development areas, and you will again get great prices for these houses because they can/may be demolished and newly built there

Then calculate these cases for yourself - in urban areas you might still manage to convert a single-family semi-detached house or a row of three, but without densification it rarely becomes a good business, because prices are still quite high. Construction anyway, and purchase & demolition as well. Especially since the heirs usually are not in a huge hurry and speculate on falling interest rates..