Drying of the new building / Mold / Ventilation

Hello everyone,

we moved into a new building in May (Energy Saving Ordinance 2009, semi-detached house).
About a month ago, it was below freezing outside for the first time, and in the morning the roof window was wet on the inside. The front door as well as several windows on the ground floor were also damp.
We are a total of three semi-detached houses, so six households. Since the other households reported similar issues and attributed it to the normal residual moisture of a new building, I didn’t think much of it.
On those cold days, we simply wiped the windows from the inside in the morning and aired the rooms briefly. For me, that was the end of the issue.

However, yesterday we discovered mold in the plastic of the roof window, in the circular recess (for clamping an interior roller blind?). There may have been a few drops of water there, perhaps we overlooked them when wiping. We immediately removed the mold. I don’t think it’s a major problem, since the mold was not directly on a wall or on wood or similar, but on plastic.

However, we want to avoid potentially getting a mold problem. Therefore, my question: How often and how long should you ventilate to generally prevent mold growth?
The construction company recommends three times a day (they even included a brochure about this at the handover), but I can’t just come home from work at noon and then drive back out again just to briefly open the windows.

How do you do it?

Best regards
StuttgartDHH

Hello.

You must ventilate at least 3 times a day or set up a drying device or find another technical solution. Window rebate ventilators, Velux double casement window ventilators, electric windows, retrofit decentralized ventilation... something like that.

Residual moisture is one thing and certainly needs special consideration. But even in dry construction, there is moisture that wants to go somewhere in winter. So the phenomenon will be of a permanent nature, even if it becomes weaker.

Grandma always said, better water on the window than on the wall. She was right.

So wipe away nicely, ventilate, and watch the typical mold corners (house corners, don't place furniture tightly against the wall, etc.). Thermal bridges can of course lurk anywhere and lead to condensation...

For myself, I make three more crosses for the ventilation system – we're still planning after all :)

But not only ventilate but also HEAT!

Especially the rooms with the skylights, I would now raise the temperature enough so that the dew point is not fallen below, otherwise welcome to the mold paradise...

Thanks already for the quick answers!

But not just airing out, also HEATING!

Especially the rooms with the skylights I would now raise enough so that the dew point is not undershot, otherwise welcome to the mold paradise...

That is a good point: The bedroom (which this is about) is tendentially more of a colder room. Although "colder" here is relative, since all the heat of the house rises anyway through an open stairwell. But we turned up the radiators in the attic again quite a bit yesterday.

I did not know about double casement window ventilators, I will google that. Since our double casement windows are also from Velux, there is surely something suitable.