Dust problem and "mold problem" at the same time

Good day forum,

we have now been living in our house (newly built, timber frame construction) for 9 years, and have actually had an extreme dust problem from the very beginning. You can see the dust flying around in the air when the sun shines, and if I were to clean now, I would see it lying there again tomorrow. I am not talking about large dust bunnies here, but rather the "dust particles."
We heat everything with underfloor heating, and recently we have also installed an air conditioning unit (or rather the split system) in each room, and since then we sometimes heat with these as well (but only marginally). All the beds are quite new, not too much furniture, and there are no curtains, instead blinds. We have also tried ventilating by opening windows briefly for a long time, but it did not make any significant difference. So it shouldn’t be these things.

For me as a layperson, this would suggest that the humidity is too low, were it not for my other problem: mold forming on the silicone seams of the windows. It is not uncommon for water to form overnight on these silicone seams. While we always try to wipe it dry, apparently without success. Slowly but surely, mold is beginning to form (especially in the corners) on these seams. Our windows are double glazed.

Could it be that the house is simply too well insulated? (Even if that might sound silly now).

As I said, I am a complete layperson in this field and would be grateful for any answers!

Best regards,
Fabian

Yes, you live in a plastic bag and have no forced ventilation. Install regel Air in the windows, and mount an exhaust fan in the bathroom on each floor. What will happen? The motor, which runs constantly, will suck air out of the house, fresh air will always flow in through the regel Air slots, and you will no longer have mold spots on the window. Dust? No idea. My wife has a Dyson, we have no dust. Karsten

Dust swirls because you have no dust catchers like carpets, curtains, etc. that could catch the dust.

Yes. Get yourselves some textiles and/or a robotic vacuum cleaner that operates at least once a day. Plenty of ventilation helps prevent mold and reduces dust in the air. An even better solution against mold is a forced ventilation system.

So if mold forms in the joints around the windows, I assume that there is a thermal bridge there. We are still missing the "joint decorations" inside and I have noticed that it drafts quite a bit, especially with compressible tape. But also with foamed joints where the foam didn't reach everywhere, air leaks through. Also at the bottom, where there is only this plastic rail on which the windows rest, there is a draft. We also have a timber frame construction (built in 1976). The windows are triple-glazed and only fog up on the outside, no mold anywhere. Inside, we still need to finish the window connections (internal insulation, with climate membrane covering the entire area, tape over the joints around the windows, and wooden battens with wood fiber boards). We also have extreme dust, but that doesn't surprise me since we have rabbits and bedding, hay, straw flying everywhere. Plus ash and sawdust from the wood stove. And of course the dust from the complete construction site. We now have an air purifier on each floor (around 50 euros) and that helps tremendously. Actually purchased because my husband now vapes instead of smoking and the vapor fogs up the place. You can still see every time you move the duvet, for example, that dust clouds actually rise up. For the summer, I will get a good old carpet beater and a mallet for the garden and then regularly beat out the blankets.

Although we have only recently moved into the new building, we have purchased two things:

a) a dehumidifier for each floor at 180 euros each (for a maximum of 72m2):

These are placed centrally. On other days, they are used only in individual rooms with the door closed. They are set to automatic so that the devices start running when humidity exceeds 65%.

b) a powerful air purifier for 230 euros that supposedly can filter pollen, mold spores, and fine dust from the air. The sensor is quite good: as soon as I have to shred something and the air purifier is nearby, it immediately detects the pollution and increases the performance. We keep moving the air purifier to different places. If necessary, we may buy a second device.

P.S.: If anyone finds this setup problematic in any way, feedback/criticism is welcome