KfW 55 - Ventilation system yes/no? - Experiences

Are central ventilation systems with heat pumps actually subsidized? Only in connection with a heat pump? What exactly does it depend on?

Yes, it is subsidized in combination with a heat pump if controlled residential ventilation and heat pump are controlled/regulated together. This can be done either via a common interface (e.g., as with Nibe) or even via smart home solutions (KNX, radio). It still applies that the annual performance factor of the heat pump must be at least 4.5. More information can also be found on the BAFA website or from Zehnder in a fact sheet.

Hello,

I actually wanted to start a separate thread at first, but this one is exactly about the topic. The situation is as follows:

For our general contractor, KfW55 is standard, regardless of a ventilation system. Our construction consultant advised against a centralized ventilation system because he is not convinced about the issue of germ-freeness. I personally have no idea how to assess this topic. What definitely speaks against the central ventilation from our point of view is the price of a mere 19,120 EUR. Mind you, that's only for the ventilation system. We are building with 200 m² of living space.

It might be worth mentioning that our general contractor is positioned in the upper price segment but also has a very good (if not the best) reputation. Still, when you see the amount, you start to wonder if that is really necessary. A decentralized ventilation system would be several thousand euros cheaper, but it doesn’t look particularly nice. Besides, we haven’t met anyone so far whose decentralized ventilation is not loud.

One of our future neighbors, who apparently has built several times, is convinced by a different approach: no ventilation system, but drying devices after completion to get rid of the initial moisture and then simply ventilating through windows.

The idea we now had which somehow connects the concepts a bit: our ground floor ultimately consists of one large room (from the front door straight through the ground floor into the living, dining and kitchen area), then the stairs up to the hallway upstairs. Would it be conceivable to simply install one or two (more powerful?) decentralized ventilation units downstairs and upstairs to at least create some airflow when no one is home? In the hallway they wouldn’t disturb anyone anyway. We could easily leave the doors to the other rooms open when no one is home. Otherwise, we are absolute fresh air enthusiasts; our windows are basically always open. What do you think about it?

KfW55

decentralized ventilation

almost always windows open

Why build an ultra-tight KfW55 building and then make holes with minimal heat recovery in the building envelope, or keep the windows open (tilted?) all day?

Topic germ freedom

How does he see the topic of germ freedom with fresh and wastewater pipes? Stagnant water is supposed to be death in liquid form.

ultra-dichten

Let's not exaggerate

KfW55-Bau hinstellen

As mentioned, because it is standard with our general contractor.

und sich dann Löcher mit minimaler Wärmerückgewinnung in die Außenhaut hauen lassen

As mentioned, because we find 19,120 EUR for a central ventilation system quite steep.

bzw. den ganzen Tag die Fenster auf (Kipp?) lassen?

As mentioned, because we are fresh air fans.

Are you building with a heat pump? If yes, do you achieve a seasonal performance factor of 4.5? If yes, apply to [BAFA] together with a [controlled residential ventilation system] (must be jointly regulated, e.g., via radio), then you will get 35% funding on the systems. This almost covers the costs for the [controlled residential ventilation system].

Otherwise, what does the energy consultant say about the [KFW55] construction without [controlled residential ventilation]? Decentralized solutions always mean that you bring the noise of the fans into the room and the heat recovery will be zero or very close to zero. But especially if you are fresh air fans, I would consider taking on the costs for the [controlled residential ventilation system].

It will be similar for us and we are probably a bit old-fashioned in that regard. I will have a controlled residential ventilation system shown to me somewhere, but at that price I would drop out immediately.
Our kids have left the house and we have an open gallery area. I think the need for air exchange is different than in individually closed rooms and separate floors with 4-6 residents.
I still have in mind the option, similar to you, to bring air into the house or transport it out through the unfinished attic. I could retrofit this afterward and practically invisibly for little money if some air exchange were necessary.
We could open windows on the ground floor and thus ventilate almost the entire house; with floor plans having several closed rooms over 2-3 floors, you would really have to walk around..... I would find that quite inconvenient.