Which KFW standard and which technology in new construction

Tom, no one wants to talk you out of a gas heating system. If we had gotten a connection here, I would have chosen one too... But now I am also satisfied with the air-water heat pump, as the heating costs have been low for two winters. In addition, the subsidies for just under 20 kWp photovoltaics will expire in the next few years. The electricity has to go somewhere then...

Our residential area was developed and sold starting in 2013 by a subsidiary of Volksbank. The first houses were built around 2014. At that time, it was unquestioned that gas was part of the infrastructure. However, in the meantime, many builders, especially in the years 2016-2017, have dispensed with gas. The gas supplier countered with a combination offer. Take connection and gas, we give 50% discount on connection. Since then, the number of boilers has been increasing. In 2017-2018, they all build with boilers. Anyone who does the math can’t do otherwise. The chimney sweep charges 96,- here every 2 years. It is negligible. Electricity is moderately expensive in SH. My tariff at eon: 10,- per month flat fee, plus 32 cents per kwh. It can be cheaper with other providers, but we are currently bound to eon because of the cheap gas combo tariff. There the base price is 5.00 per month plus 4.8 per kwh. Karsten

Nordlys there are simply people who want to be independent from energy suppliers. For whatever reason.

Thank you for the many tips, hints, and suggestions. I think it will now come down to KFW 55 with gas, solar thermal, underfloor heating, and ventilation. Only with the ventilation am I still unsure. For me, window-frame ventilation is out of the question. In your opinion, is decentralized ventilation only in the wet rooms sufficient? That would be the utility room, kitchen, and bathroom downstairs, and the bathroom upstairs. That might be a bit weak, right?

I would not build without a central ventilation system nowadays. If it is supposed to be efficient and quiet.

Facing the same decision as the creator of the thread, for us the reasons are economic in nature:

Both are in their late 30s or early 40s, so the house must be paid off in 20 years without the monthly rate causing sleepless nights.

Underfloor heating is a must for us, as well as controlled residential ventilation with heat recovery.

Gas condensing boiler is the standard with the house provider. An air heat pump costs an extra €10,000~12,000, which in my opinion is a rip-off.

Gas is available at the doorstep, and the gas house connection is €399 up to the house because the supplier subsidizes it.

For the extra cost, I can get a lot of gas. But I am already planning the underfloor heating for a later switch to an air heat pump.

But I wonder (because I don't understand all the KFW stuff) if I can still achieve KFW 55 with just a gas condensing boiler and controlled residential ventilation with heat recovery? Or do we necessarily need solar thermal to secure the KFW 55 status?

At the same time, for reasons of comfort, we would also like a circulation system, but according to the house manufacturer, that could cause the KFW 55 status to be lost? Or can you safely do without circulation in a bungalow with 110m2 and one bathroom plus a guest WC?

I don't trust these super great 3-liter rules on paper/mounting plan regarding the actual pipe routing and dimensioning on site...

Well, questions upon questions...