KfW 55 or 40+ for new single-family house construction in Würzburg?

Buffer storage for heating and also for photovoltaics out..
These are just additional costs that never pay off.
Unless you do the photovoltaic storage out of love for it

And then invest the saved money in insulation etc instead

That's true, that's a point I wanted to discuss next week with the plumber who is preparing the specifications for us. Also no bypass valve, no individual room control (although mandatory, but you can get exempted)? Better a proper hydraulic balancing and minimal costs in purchase and operation. Self-regulating effect of underfloor heating.

But of course, the question remains whether the additional investment of 14k in insulation will really pay off at some point and whether we are unnecessarily inviting problems into the house with the ETICS (if it has to stay that way).

And, if money is no object, plan the roof with wood fiber boards as external insulation, combined with insulation between the rafters. Expensive, but qualitatively the highest quality.

Or do you have a cold attic with insulation on the top floor ceiling?

Well, the money is of course not exactly loose. Why should I do that, what advantages does it bring?

The insulation is planned in the roof so that we might still be able to convert the attic into one or two rooms later..

Well, if the attic is later converted, the wood fiber boards would be a great advantage, as they provide significantly better heat protection in summer.

Attached is an excerpt of the preliminary draft of the insulation values, I hope you can make something of it, I as a layman not so much..

There is still quite a bit that can be done on the exterior wall, the architect has already chosen the right point of attack there. Possibly also on the walls hidden in the ground, more perimeter insulation, etc. In that respect, the architect's suggestion doesn't sound wrong at all.
Why do the walls have so many different U-values? What material has been planned so far? T8 with 30cm, I assume?
Windows with a lower U-value would also be an approach, but that is usually a more expensive pleasure.

As I said, try calculating monolithic KfW40 and KfW40 with 24cm bricks or even sand-lime bricks plus thick ETICS, it could be significantly cheaper.

As said, let's calculate KfW40 monolithic and KfW40 with 24 cm bricks or also KS plus thick ETICS, could be significantly cheaper.

Okay, I have passed this task on to my architect, I will get back to you. My brother-in-law (building expert) explicitly advises against ETICS, as it only lasts 25 years and not 100 years when the insulation is in the stone..

Which material has been planned so far? T8 with 30cm, I assume?

Bingo!

Best regards and many thanks

Okay, I passed this task on to my architect, I will get back to you. My brother-in-law (building surveyor) explicitly advises against WDVS, since it only lasts 25 years and not 100 years, if the insulation is in the stone..

A friend who is an architect also strongly advised us against it. I was able to look at another house where the polystyrene blocks were glued and plastered, and I then ruled it out for us. You build a house from stone and then stick thick and large-area plastic on it.

When I now look at the current pictures of the underfloor heating on the ground floor, then our fight against polystyrene was not consistently successful...

Hello everyone,

we are currently facing a similar decision - KFW 55 or KfW 40 plus.
The photovoltaic system is planned and will be installed in the house regardless of the standard. The power storage is also planned so far.
We are still undecided about the ventilation system. We could manage without it at KfW 55, but not at KfW 40 plus.
A heat pump is planned as our heating system. We are currently waiting for offers for an air-to-water heat pump or one with trench collectors. What it will ultimately be depends on the offers.
What is much more important to us, however, is the insulation.
We are building solid with a 42.5 cm stone. Currently, a 009 brick (U-value 0.20) is planned. For an additional cost, a 42.5 cm stone with 008 (U-value 0.18) would also be possible.
It is important that we do not need additional ETICS. Does anyone have experience with this and can tell us whether this is realistic?

Thank you very much

P.S.: I hope it’s okay that I’m “joining” this thread, as we have a similar topic. Otherwise, I’m happy to start a new one.