Construction costs are currently skyrocketing

And if you don’t do that, you have to buy it expensively through the [Kontrollierte-Wohnraumlüftung]. I prefer to ventilate and save that money. And I don’t understand those anyway who clutter their floor-to-ceiling windows with everything. Better fewer windows and proper space to place things. But to each their own.

For us, decentralized ventilation was mandatory for the house and cost 6k€. We didn’t upgrade much, but I definitely wanted the central air system for an extra 6k€. Not having to ventilate ever again is a pretty nice thought. When using a fireplace in the living room, is the heat actually transferred to all the other rooms? I only know that through air exchange, pretty much the same climate prevails in all rooms. It would be nice if you could heat the entire house additionally with the fireplace heat.

When using a fireplace in the living room, is the heat actually transferred to all other rooms? I only know that through air exchange, pretty much the same climate prevails in all rooms. It would be nice if you could additionally heat the entire house with the fireplace heat.

No, it is also easily derivable by calculation. (Air 20°, 1.2kg/m3 at 1kj/kg*K)
Rather through heat radiation from walls, e.g. aerated concrete interior walls, provided they were built solidly.

Exactly. With a fireplace, not only the entire living room and hallway heat up for us, but the bathroom also gets warmed at the same time, but only because the chimney runs along there. And the warmth from the stove is really quite special. Especially when it is very cold. It cannot be compared to a normal heater.

Just walk around and look at houses and apartments. The amount of "decorations" and plants on the windowsills is astonishing. Then maybe also curtains and drapes. Nobody clears all that stuff away several times a day to properly cross-ventilate. Instead, the windows are tilted open – I have already seen nice mold cultures on the window sill, cultivated that way.

In this respect, a ventilation system is more than just "nice to have," because many people simply do not ventilate properly.

You don't have to clear everything away if you decorate properly. I have several large windows in the living room; in winter, the plants that will go outside in summer are standing in front of some of them. But it doesn't matter because it is enough to open just one window properly to ventilate. The same applies in other rooms; we have double-wing windows, so only one wing is opened, which is sufficient. Curtains don't have to be pulled aside for ventilation if they are correctly installed. Only drapes may have to be drawn back if necessary. But many people don't even have those anymore today.

We also ventilate. And gladly so. We have installed windows with fixed bottom lights specifically for more comfort. That way, you can ventilate and at the same time leave the decorations in place. Problem solved.