Purchase decision small semi-detached house 100 sqm from 1930

What is considered normal ventilation? Theoretically, you have to ventilate three to four times a day for 30 minutes. Probably no one manages that. So if normal means according to the standard, then as much as possible (officially you have to have a ventilation concept created). If normal means commonly usual, then probably ventilating in the morning and evening for 15 minutes each is enough, but then cross-ventilate.

Even 15 minutes is already very long. I, for one, don’t want to sit on the cold train during breakfast and then you still have to squeeze it in somewhere. For me, that is usually next to brushing my teeth and then we only talk for about a third of the time. Important against mold is not only ventilating but also heating properly. Otherwise, you have a low dew point and condensation on the wall.

We also don't air out for 15 minutes in winter, otherwise the place would be cold. A few minutes of good ventilation and done. As long as the heating is off, I air out much longer.

We also don't ventilate for 15 minutes in the winter, otherwise the place would be cold. A few minutes with a nice draft and that's it. As long as the heating is not on, I ventilate much longer.

That's how it is for us too. In the morning, go through the house, raise all the shutters, open all the windows, brush teeth, put in contact lenses, close the windows again. During the day, you open the front door quite often. In the evening, do the same again. Completely sufficient.

In the cold season, it's quite easy to "ventilate properly." You open the window, it fogs up on the now inward-opened outer side of the window, and as soon as the glass is clear again, you can close it. Depending on the humidity, it takes more or less time. Brushing my teeth is never long enough... more like a full 10 minutes. Oh, and the room being cold afterward isn't really true either. Sure, warm (and moist! that's why you do it) air is lost. But the walls, furniture, etc. are still warm. Reheating the air doesn't take long.

Brief update: After about 11 months of major renovation, much of it done by ourselves, we are now living in our small semi-detached house. We completed the entire renovation for €135,000, having already deducted €13,000 in subsidies for the roof, windows, and front door. However, some things still need to be done: the terrace still needs to be redone, the facade will get a new coat of paint, and the garage including the garage door still has to be finished. I estimate another €17,500 will be needed for this. Including the purchase price and incidental costs, we would then be at about €280,000 for our first own property. :) Almost everything was done; in the end, only the walls remained, everything else was replaced and brought up to today’s, I would say medium, standard (e.g., no KNX, but at least network sockets). It was a very challenging time, six days a week on the construction site, usually until 9-10 pm after work, and Saturdays entirely—fortunately, I had my very talented brother-in-law by my side, who has built before and is pretty skilled with his hands. Without him, it certainly would not have been possible. But I learned a lot. It’s certainly not perfect, but pride prevails for now. :) Pictures to follow.