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Now that the temperature outside has dropped, the windows start to accumulate water vapor. I am assuming that it might also lead to that black stuff forming. Is there a more efficient way of dealing with the condensate than wiping it dry every day?
I’d suggest using a dehumidifier. Alternatively open the windows once or twice a day to reduce the humidity in the room where this is happening.
Dont use a dehumidifier. Just open the windows to let humid air out and fresh air in.
A dehumidifier can help a lot when the room is barely heated. This is also the case when insulation of the building is bad. Some apartments will always be humid, even when opening the windows everyday. In those cases a dehumidifier will do the trick and you'll get about 2 - 3liters of water out of the room within a couple of hours.
You have to adopt the concept of "stosslüften" to get rid of excess humidity in your room. Warmer air carries more water, but it condenses on cooler surfaces Like outside Walls or Windows, the Window is the better Option because wet Walls get moldy soon. You also should make shure that there are no big furniture or other items without space to an outside wall if the building ist Not well insulated.
Couldn't solve this as well so far. Looking at it with a thermal camera in cold weather revealed insufficiently insulated windows as the root cause. Basically the frame holding the glass sandwich itself is thermally too conductive at the seam, which tends to be a lot colder than the rest. If the difference is too low, condensations forms depending on the current dew point in your room. As a rule of thumb, if you have 22°C inside and 59% relative humidity, you have a dew point of around 14°C. If your insulation on the windows gets below that, humidity condensates there first. Airing out the room can help lower the dew point, but usually that's barely enough.
The only fixes to lower the dew point are reducing relative humidity to inhumane levels (below 30% relative) or increasing the room temperature by alot (more than 25°C), all combined with several airing out of the room for 5 minutes 3x daily all winter.
Other things to do are identifying and monitoring high-humidity rooms nearby. Most likely your bath with a shower inside. If you have a "dark bathroom", meaning now windows and just a vent, switch the vent for a humidity-controlled version and dial it in on around 63% humidity. Install a vent in the door near the bottom as well if not existent already, since a closed door chokes the vent. Once the door opens, water vapor enters the flat/house and raises the humidity quickly.
The only ultimate solution to this is replacing the entire windows with three-panel versions in properly insulated frames, reducing constant water vapor sources like in baths and kitchens using whatever venting methods work best there and lastly (most likely impossible due to cost if you are not considering building a new house) switch from traditional radiation heaters to an air conditioning heating/cooling solution which levels out most of the humidity issues electrically.
This is a detailed answer with which I largely agree, I just want to point out that the installation of better insulated windows shifts the problem in insufficiently insulated buildings to other areas, often the moisture then settles in corners and leads to mould there - in the past it was said that the window should always be the coldest surface in the room, today there are Ventilation, insulation,... but i think this is still a good rule
The black stuff is mold and it's both, a health hazard and it eats away the gasket.
It's best practise to keep temperatures at least at about 16° C at a relative humidity of at most ca. 60%. So set your heater in the room accordingly. Possibly you need to go a few degree higher. A thermohygrometer can help to keep an eye on the temperature and humidity. If the humidity rises above 60%, it's a good time to open the windows to get rid of excess humidty in the air. (~~That does work of course if it's rainy outside, i.e. even more humid.~~ See correction in comments by @Mrs_deWinter.) For air quality resons, ventilating rooms a couple of times per day is a good idea anyway.
You can find more resources on that topic if you search for mold prevention in residental buildings.
Edit: Striked an incorrect statement, referred to correction.
temperatures at least at about 16° C
Which should be 2 on thermostats
That is, if the heating system is corrctly sized for the space your heating and adjusted to current weather.
(That doesn't work of course if it's rainy outside, i.e. even more humid.)
It works even if it's rainy outside. The relevant factor is temperature. Warm air traps much more humidity than the cold air outside - even if it might feel humid there. When we open the windows our saturated warm air gehts switched with saturated cold air, which then warms up inside and increases it's capacity to absorb humidity in turn.
As long as it's colder outside than inside ventilation will get rid of a room's humidity.
5-10 minutes is perfect: It allows for a significant air change and doesn't cool down the room (floor, walls, furniture) too much, so as soon as you close the windows again the temperature can quickly rise and allow for the desired dehumidification.
Thanks for the correction. :)
Stoßlüften.