ᐅ Decentralized ventilation only in individual rooms for new construction to KfW 55 standard?

The question of why a controlled residential ventilation system is needed feels to me like asking: why a washing machine... you can also wash clothes without it, and that's cheaper.

Yes, that's true, and a controlled residential ventilation system probably doesn't pay for itself, but having fresh air all the time is so great.

If a central system is not possible due to cost, then I would only install it in the bathroom...

For continuous operation in bedrooms, the devices are too noisy for me.

We deliberately chose a central mechanical ventilation system with heat recovery because I work full-time and my wife is studying, so we are hardly at home during the day. Manually ventilating the house would not be feasible for me. It costs us an additional 14,000 (approximately), and I didn’t consider payback when making this decision. In fact, I had to give up something else for it (which can be easily added later if needed), but it was worth it for us.

For me, with the mechanical ventilation system, the key factor wasn’t payback or anything like that, but rather the benefits it provides—and I get quite a lot from it...

I’ve also spoken to other homeowners who have one. They are glad they installed it, and everyone I know who chose not to include it in recent years now regrets that decision.

Central mechanical ventilation with heat recovery only; otherwise, it is better to have no system except for bathroom exhaust.

Why only central?
If I install a decentralized system in the bathroom, pantry, and utility room and ventilate the other rooms separately, that should be fine, right? And from a cost perspective, it would probably make sense as well?

Erik1990 schrieb:

If I install a decentralized system in the bathroom, pantry, and utility room, and ventilate the other rooms separately, would that work?

If you decide at all in favor of “controlled residential ventilation,” the choice between “centralized or decentralized” is a fundamental principle-level question, similar to network topology or, by analogy in IT, the difference between a standalone PC and a client/server setup. We have already discussed this principle here, see: https://www.hausbau-forum.de/threads/lueftung-im-Neubau-zentral-vs-dezentral-geraeuschbelaestigung.16160/

Choosing a decentralized controlled residential ventilation system just to selectively install it in individual rooms—based on a pro or contra approach per room—like “we’ll only use it in rooms where there is a high risk of mold growth if we don’t ventilate regularly enough,” is, in my opinion, a misunderstanding of the technology. Controlled residential ventilation is not a mold prevention system; it is a ventilation technology. Using it selectively only in so-called “high-risk rooms” is misguided.

Therefore, I recommend making a consistent decision either in favor or against controlled residential ventilation throughout the whole building. The decentralized solution is not intended to allow you to omit it in some rooms (with the naïve assumption that, say, fewer than two-thirds of the rooms covered would be cheaper overall). Rather, it is a matter of principle: a single-room solution is like a “single workstation solution.” Each standalone unit must be individually sized, is not networked with the others, cannot pool its capacity, and requires all components for each unit. Its advantage compared to a central system is precisely the lack of networking (which, as an advantage of the central system, saves the ductwork network between rooms).

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I personally see decentralized systems as a last resort. I tested some systems and found them disturbingly noisy, especially during switching times. That’s just unacceptable. I have no idea how anyone could sleep with that.

I would rather have no controlled residential ventilation than a decentralized system.