Decentralized ventilation system experiences

Hello everyone,

my wife and I are currently planning the construction of our single-family house with about 140 m2. Our construction company has now presented us with an offer that includes a decentralized air-to-water heat pump in the standard version, about which there are different opinions here in the forum. Alternatively, we also have the option of choosing an exhaust air heat pump with controlled heat recovery (additional cost around 6000 euros) or a controlled residential ventilation system as a central unit (additional cost around 14000 euros). Since we are currently still undecided whether to build according to the KFW 40 standard (for cost reasons), we are torn back and forth about which variant we should choose. We assume that the central system is probably the "best" in terms of comfort. For financial reasons, however, we would like to see if one of the other two options is also suitable. Specifically, we are interested in the following in this context:

1.) What are the noise emissions of a decentralized system? Would you, as builders, choose such a system again?
2.) What is the added value of a decentralized system compared to a controlled central residential ventilation system with heat recovery? Is that even a "real" alternative to the decentralized system?
3.) Is a controlled residential ventilation system a prerequisite for KFW 40 funding? If yes, is the middle variant costing 6000 euros sufficient for that or is the larger one for 14000 euros required?

If you have any further ideas or suggestions, always feel free to share!

the standard version includes a decentralized air-to-water heat pump

1. The central version is the best (and most expensive) option.
2. Central should be standard in new buildings.
3. Decentralized is ideal for renovation (I have it in the current house).
4. Decentralized is visually conspicuous and also always (significantly) louder.
5. In effect, both are the same.

Are the decentralized air heat pumps only for heating/cooling or also for ventilation? Is underfloor heating not planned at all?

Decentralized and wind noise plus electricity consumption, such things cannot be willingly tolerated in a new build. Depending on the region, the units run at full capacity in winter.

Look at the Facebook pages of Weberhaus and Schwörerhaus. There are plenty of affected people who are surprised.

If anything, then central with heat recovery and air-to-water heat pump.

1.) What are the noise emissions of a decentralized system? Would you, as builders, choose such a system again? 2.) How much added value is there from a decentralized system compared to a controlled central residential ventilation with heat recovery? Is it even a "real" alternative to the decentralized system? [ << ] Since we are currently still undecided whether to build according to KFW 40 standard (for cost reasons), we are currently torn back and forth on which option to choose.

1. Decentralized systems cannot pool, so in practice they always operate with higher efficiency losses overall because each subsystem (and all combined) more frequently operates "outside the optimal speed range." Their noise emissions at different positions not only add up to be overall higher than those of a central system, but they also interfere with each other. Simply put, they therefore sound "louder" and "more unpleasant." 2. Decentralized systems only make sense where they are not meant to serve the entire building, but where controlled residential ventilation is intended only for certain parts of the building — especially when the "unserved" areas outweigh the "served" areas. 3. The EH40 standard will only be cost-effective for "normal consumers" with the perspective of "pensioners at the end of time." If you are better earners, if capital income and tax effects contribute more to your asset accumulation than income from salaried work, and if you have reason to see yourselves as eco-avant-garde role models in your social circle, then go ahead with EH40. Anyone who believes that KfW should enable normal earners to act this way is dreaming.

1. decentralized systems cannot pool, therefore they practically always operate with higher efficiency losses in total because each subsystem (and all in total) more frequently operates "not in the optimal speed range".

... must of course be operated / operate.