KfW - construction: is it necessary or not?

I believe the resale value is a completely overrated argument.

Not quite. The classification whether KfW 55 or Energy Ultra really doesn't matter to anyone, to put it bluntly. But everyone will look at the actual energy consumption. And no builder should lose sight of that. I know enough KfW70 houses (which no longer exist) that are cheaper to heat than a modern KFW40 house, which was just nicely calculated but whose air-to-air heat pump causes immense costs.

Exactly. I have heating costs of around 60€ in our Kfw 70 house. That is 7500€ in 10 years. So where is the huge price difference to KFW40 or KFW55 upon resale supposed to come from? That is peanuts compared to the house prices and associated financing rates. No matter what the classification is, these have all been low-energy houses for years.

@pagoni2020

To ask why something doesn't pay off and suddenly should just because politics changes a parameter,...and to ask why a difference in the building envelope and thus a greater heating energy demand should make no difference.
Some might even maliciously say that you only need to promote what hardly anyone would buy otherwise. That is why I deliberately use electric cars as an example.

At the latest, the annual performance factor values create facts here.
With photovoltaics, no efficiency will change anymore, as space research has been working on this for too long. Lithium batteries are completely excluded.

My recommendation for action would first depend on whether a gas connection exists at all, which heat pump is to be used with which annual performance factor, and which subsidies are involved.

Otherwise, the leeway here is limited with KfW55, so I would always tend towards the most optimal building envelope possible, because the current heating technology is far too fragile to last long. A look at China, which is about 5 years ahead here, shows what will be possible in the future with hydrogen.

@Musketier

Forget the heating costs; those are sales figures, the space heating load is decisive here.

Forget the heating costs, those are seller's information, the heating load of the room is what matters here.

When selling an existing property, I am only interested in the actual consumption.

@Musketier

Forget the heating costs, those are seller's information, the heating load of the room is decisive here.

You were never looking for a used property, were you? I hardly believe that the seller will have the heating load of the room calculated for you when there are still 5 other couples standing outside.

What would you consider the logically sensible recommendation for a home builder in 2020?

Make confident decisions and build the way you want instead of stretching for subsidies. Build one or two sizes smaller than you could. Think about the quality of life during the years in the house rather than building for a fictional future buyer. Stay relaxed, hire local craftsmen, and enjoy the construction period. Simply don’t let others stress you out about how "people" do things nowadays while staying interested in technology and methods. It’s actually not difficult.