Change heating "after" building permit?

To be honest, I imagined it to be that simple as well.

Until the email from the energy consultant came: "not nearly enough"

It is not a general feat, but compared to the version with an air-water heat pump heating system, unfortunately, it is. That is, by the way, the unfair part. The house heated with an air-water heat pump is allowed to waste so much more heat than the house heated with gas and is still a KfW55 house... :-(

It is built massively, even kfw55 without controlled residential ventilation but with insulation and solar. And I consider the claim that a house with controlled residential ventilation wastes more energy to be a rumor.

Of course, that's possible. We also have gas + solar + centralized controlled residential ventilation and have, by calculation, a "Kfw 60 house".. so we didn't reach KFW55, but we're closer to the KFW55 values than to the KFW70 values.

If, in addition, a perimeter insulation were installed under the basement floor slab, along with thicker insulation on the basement walls and thicker exterior walls (we already have TV7 bricks), that should easily be enough.

Whether it is financially worthwhile, I would cautiously doubt.

How important is KFW 55 for you as builders? Is it really about, well, everyone does it? Or about, well, you just have it, like a leather steering wheel in a Golf? Or is it about the subsidy and the loan? Or about genuine ecological concerns? The latter? Then please go straight for 40+. Otherwise, what others have or what one just has doesn’t matter. And the subsidy? It eats up the surcharge for air-water heat pump compared to gas with solar. And the loan? It’s not particularly cheap, you can also get a bank loan at that interest rate. Conclusion, KFW 55 gone, gas and solar are no problem at all. K.

How important is KfW 55 to you as builders? Is it actually about "well, everyone does it that way"? Or about "that's just how it is," like a leather steering wheel in a Golf? Or is it about the grant and the loan? Or about genuine ecological concerns? The latter? Then please go straight to 40+.

Or does the development plan require KfW 55?

That extra cost of an air-to-water heat pump is eaten up by gas with solar.

Do you even read? The builders don't want an air-to-water heat pump right now.

The only extra cost for KfW55 in the end is the controlled residential ventilation, and it basically finances itself from the KfW55 subsidy (5000€). So, free of charge.

If you want to build a well-insulated house anyway, for whatever reasons: increased personal comfort temperature well beyond 22°; open spaces with air gaps between floors; no windcatcher in the hallway, etc. etc.

Then why not take advantage of the KfW55 subsidy?

Presumably KfW55 today = the next energy saving ordinance tomorrow, building like this now can't be wrong.

Of course, if you have to pay extra for wall construction, subfloor insulation, etc. just to achieve KfW55, then it’s not worth it for you.