Why Does My Window Grow Mold?


Windows, like many household surfaces, can develop mold and mildew. Like all mold, you should take window mold seriously and make an effort to eliminate it right away, as it can spread to other parts of your home and potentially lead to serious health problems. Mold can grow on a window for numerous reasons.


  • High relative humidity is a leading cause of mold growth in households. Humidity serves as a unit of measurement for the amount of water vapor in the atmosphere. This moisture can settle on surfaces such as wood, upholstery and also glass. For example, if you have ever worn a pair of glasses that became foggy on a very humid day, you have seen this principle in action. When moisture penetrates glass for an extended period of time, mold spores can potentially germinate.


  • Condensation also provides the necessary moisture for mold to grow. On cold mornings, moisture collects on windows, but it usually evaporates as humidity falls and sunlight penetrates the glass. Certain circumstances, however, may prevent the moisture from evaporating. For example, if the glass has cracks that trap moisture, or if cold weather conditions prevent moisture evaporation, the condensation may linger for an extended period, thereby allowing the necessary time for mold growth.

Dirty Glass

  • If your window has layers of dirt, it has an increased risk of developing mold. Soil provides nutrients for mold spores, and a dirty household surface can breed mold, according to a University of Missouri report. Keep your windows clean to reduce their chances of developing mold. If your window develops mold at any time, dust accumulation must play a role, because glass itself does not provide mold spores with their needed nutrients.

Removing Mold

  • Glass is nonporous, and therefore you can remove mold from a window with much greater ease than you would from a piece of wood or upholstery. Spray the window with a glass cleaner containing ammonia. Ammonia provides powerful disinfection against mold and will also leave your window much cleaner. As an alternative, you can spray the window with full-strength vinegar. Allow your liquid to remain on the window for a few minutes, then dry.

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