I assume it is due to unwillingness. Maybe the house here is calculated so precisely that the construction company fears it will no longer achieve Kfw 40.
If he still wants it after consultation, then it just goes in. Boom.
You said it! AFTER a consultation. It might sound arrogant, but in this case I had the impression that the manufacturer's side also needed consultation (neither the hybrid function was taken into account, nor the correct dimensioning of the air exchange with 8,000m³).
That is correct. The service description is a positive list. It is very difficult to deduce the manufacturer's stance on decisions not yet made from it. Strictly speaking, the manufacturer could also refuse a recirculation hood because they did not promise it at the time of contract conclusion.
Well, the manufacturer is basically right. KfW40 and a big hole in the wall with a killer fan in front of it really don't go well together. That wrecks the entire energy calculation, from the controlled residential ventilation to the chimney sweep. Modern hoods with activated carbon filters also work perfectly fine in recirculation mode.
I have seen ventilation systems recently where the exhaust hood can be connected. I don't know how this complies with KFW40, but I would simply ask the manufacturer.
I could name a manufacturer where I have seen it, but I don't know if it is allowed :confused: