Klara Geywitz is the federal building minister, but you could also see her as an ambitious mathematician.

For a year she has been trying to solve an equation that seems downright insane.

Their success will determine whether there will soon be more living space in Germany or whether it will become much scarcer and more expensive.

The Geywitzsche equation goes like this: On the one hand, the SPD politician should provide more affordable housing.

And on the other hand, it should make the real estate industry more climate-friendly.

The latter succeeds above all through higher circulations – but these make houses significantly more expensive.

On the other hand, affordable living space can only be created if construction costs fall.

This conflict of goals is one side of Geywitz's problem.

She tries to advertise part of her solution on a sunny autumn day in a residential building on the outskirts of Berlin.

A Berlin housing association has added three new floors to a classic GDR prefabricated building.

It's called densification. At the top, on the eighth floor, Geywitz sorts himself in front of the cameras.

"In view of climate change, we have to build in such a way that each generation does not always seal more areas," she says and then praises the environmentally friendly wood-hybrid construction method.

Geywitz, 46, with her gray short haircut and horn-rimmed glasses, speaks as she looks: reserved and goal-oriented.

She then sneaks through the rooms and across the balcony with the mayor of Berlin, as if looking for a flat.

Nice here, the view goes far over roofs and trees.

This is how the equation should work

Facilitating such roof additions is part of their ambitious action plan.

With an alliance of associations from the construction and real estate industry, representatives of the federal states, but also environmental and tenants' associations, she has developed 187 measures intended to make construction easier and cheaper.

Financial support, reducing bureaucracy, digitization: this is how the equation should work.

Because on the other side there is the magic number of 400,000 new apartments every year.

The federal government has set this as its goal.

But the stricter the environmental regulations and the lower the rent and square meter prices, the less it is still worthwhile for the real estate industry to build.

In addition, something has been brewing for a year that makes the equation seem even more unsolvable.

Unexpected jump in costs

Until the summer, the problem for real estate manager Steffen Helbig was still a long way off: in Ukraine, on the commodity markets, somewhere in the future.

But in July he suddenly found it on his desk.

Helbig is head of the housing association Berlin-Mitte (WBM), one of the six state-owned real estate companies in Berlin.

They should build the affordable apartments that are urgently needed in the capital as well as everywhere in the country.

Now, however, Helbig received the news that one of his new buildings was going to be 10 percent more expensive - even though all the contracts had long been signed.

Such an unexpected jump in costs can bring a plan to collapse.

The entire construction and real estate industry is in the same situation as Helbig.

The war in Ukraine has caused energy costs to skyrocket.

Building material prices have also risen drastically since the summer of 2021.

Add to that the high interest rates on loans.

How are you supposed to plan today if everything is no longer valid tomorrow?