December 16, 2025, 11:53 am | Read time: 2 minutes
First impressions count! That’s why the condition of a house facade is very important. A disruptive factor can be black spots on the facade, which can form over time, especially above windows. They are actually avoidable, as they are related to a ventilation error.
Not Paint, but Algae, Moss, and Mold
Black spots on the facade above windows are a common problem. Sometimes it’s just a light gray haze. In other cases, it’s a noticeably black area. The discolorations on the house facade above the windows strongly resemble mold spots that can form inside a building. Not without reason: they are actually deposits of algae, moss, and mold fungi.
Improper Ventilation Leads to Black Spots Above the Window
It’s noticeable that the black spots on the facade form especially above windows. Why is that? The mold and mildew spots are related to the habits of the people living behind the windows. In many cases, the deposits can be traced back to improper ventilation. Although many windows have a tilt function that many find convenient, it’s better to open the window wide for ventilation. Those who ventilate exclusively or predominantly with a tilted window must expect black spots on the facade above the window.
The warm and humid indoor air rises through the tilted window and hits the colder wall area above the window. Due to the temperature difference, the air condenses there. The condensation is the ideal basis for moss, algae, and mold fungi to settle–just like on the window when condensation forms there. Facades with thermal insulation are particularly susceptible to this damage pattern because they minimize the heat flow from the building. Therefore, the facades are colder.
How to Quickly Get Rid of Stubborn Green Algae
How to Properly Ventilate Your Bedroom
How Can You Remove the Black Spots?
Since the black spots on the facade above windows are a biological contamination, you don’t need to paint the house immediately. If they are at heights you can reach with a ladder, you can remove the mold deposits with vinegar, baking soda, or soap. A pressure washer can also help remove the traces.
If larger areas are affected or the spots are stubborn, it’s advisable to hire a professional to clean the facade.
Avoid Black Spots by Ventilating Properly
To prevent the black deposits from reappearing or worsening, you should ensure proper ventilation. Avoid tilt ventilation. Ventilating with an open window is more suitable. This is especially important after cooking or showering.