Extractor hood: recirculation or exhaust air for KFW55?

Very briefly: hybrid hood, if a chimney is present. Exhaust air in summer, but recirculation in winter

Hello,

we had also thought about it for a long time but have now decided on a recirculating air system. We will have a kitchen island with a Bora. Currently, we have a simple recirculating hood from Ikea here and that works as well. It’s also a question of priority and how much it is worth to someone.

Maybe we just don’t find the smells that bad, everyone has a different level like, for example, with soundproofing.

In summer I hopefully have all the windows open anyway or am always grilling. LG

Sorry, the exhaust air would be directly on the outside wall, you would only have to make a core drill hole.

I talked to the developer.
He "is not allowed" to offer me that because otherwise he would lose the KfW55 certification.

He says because a lot of air is blown outside, you no longer achieve a KfW 55 house on paper.

But he also said he had the drilling done afterwards for himself.

But if KfW found out about it, we would have a problem.

There is no better. You have to decide for yourself what is more important. Odors can also be effectively filtered with a good recirculation hood.

there is indeed an evident difference (and thus an better):

If the recirculation system is part of an integrated ventilation system with waste heat recovery,
this can lead to problems.

Cooking fumes often contain, in addition to water, a higher proportion of fat aerosols.
These can settle in the cooler exhaust air heat exchanger and gradually
gunk it up and render it ineffective. So often disassemble, clean in surfactant bath and change filters.
Quite an unpleasant procedure!

The answer therefore depends on the usage scenario.

Sorry, the exhaust air would be directly on the outside wall; you would only need to make a core hole drilling. I spoke with the builder. He "is not allowed" to offer me that because otherwise he would lose the KfW55 title. He says that because a lot of air is blown outside, you no longer achieve a KfW 55 house on paper. But he also said he had the drilling done afterward at his place. But if the KfW found out about it, then we would have a problem

Mmmh.... I tend to think he’s just not willing to do it. But I don’t know the background. If it’s really a close call that he wouldn’t make it otherwise, you could consider options with the energy consultant that would compensate for it. But it won’t help you. It will be too much effort for him.

He "is not allowed" to offer me that, otherwise he would lose the KfW55 title.

He simply doesn’t feel like it. Nothing more. Blower door certified wall box (and ideally a model like the Thermobox from Naber) and that should be fine. Unless everything is already calculated so tightly with you that every little thing makes everything collapse. At least there are no prohibitions from KfW.

He says that because you blow a lot of air outside, you can no longer achieve a KfW 55 house on paper.

But he is allowed to install windows that can be opened, even though you blow a lot of air outside? That statement is factually nonsense, as this "blowing air outside" does not even enter into the calculation. The wall box is absolutely airtight—just like the wall or the windows (should be). Only the 15x15cm for the core drilling is less well insulated (the aforementioned wall box has a U-value around 2—for a hole in the wall that’s already good, old windows are often worse).