Mr. Walberg, Germany should become climate neutral by 2045.

As an engineer and architect, what do you say: will it work with a view to the real estate industry?

Christoph Schäfer

Responsible editor for economy and finance online.

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It can work.

However, the capital required for this is currently underestimated.

The research department of the Bundesförderbank KfW assumes that investments of around five trillion euros will be necessary to make Germany climate-neutral across all sectors by 2050.

That is calculated far too low.

For the building sector, for example, KfW estimates “only” 636 billion euros.

What is needed, however, is at least two trillion euros, more likely four trillion.

So we have to put an end to the methods of the past.

What do you mean by that?

We are trying desperately to bring the buildings down to a low energy standard.

This old idea of ​​efficiency is in principle not wrong, but the effort to make such a large part of the buildings in Germany more efficient is simply impossible.

We have been investigating the success of modernizations with the state government for years, and the marginal utility is already getting smaller and smaller.

The energy requirements of a house and its thermal insulation are specified in efficiency classes.

From old buildings to passive houses, which efficiency class makes sense?

Everything under the Efficiency House 70 is uneconomical.

Why?

It's about how much energy a person uses who lives in the building.

And below the efficiency house 70, the effect is barely measurable if I continue to raise the energy standards.

Anyone who lives in an efficiency house 40 will generally not consume significantly less energy than someone in an efficiency house 70.

So the building sector would not be carbon neutral even if we all lived in a passive house.

Yes, that is exactly the big mistake!

A building simply cannot be brought down to zero energy consumption!

Even in a passive house, the energy consumption is not zero.

As with all other buildings, there is also a need for heating.

Theoretically, it should be a maximum of 15 kilowatt hours per square meter in a year, in reality it is usually 30 to 40 kilowatt hours.

In addition, the water has to be heated, you also want to bathe, shower and cook.

And how do we become climate neutral?

You do not get the energy consumption off completely.

And the potential for savings tends to be overestimated.

The key task is to get the energy from green sources.

We need enough energy from decarbonised sources before we can achieve climate neutrality.

That is why it is simply nonsensical to keep increasing the demands on buildings, it is simply a misallocation.

So, above all, do we need more green electricity?