Causes of Window Mold and How to Fix It
September 2, 2025
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Mold in the home can cause many problems, including damage to your property and your health. Breathing in mold at home can lead to a stuffy nose, sore throat, skin rash, burning eyes, and more. Additionally, mold looks bad, and if you're trying to sell your house, it can devalue your home.
If your home has mold, remove the mold as soon as possible and take steps to prevent it from returning. Old windows are one part of the home where mold can develop. Temperature changes that occur around old windows as well as the moisture and humidity found near windows can contribute to the buildup of mold over time.
Mold on windows can be fixed, often through window replacement. In this article, we'll talk about how to identify mold on windows and discuss how window replacement and installation can prevent this problem from happening in the future.
What Causes Mold on Windows?
Are you wondering: why is there mold on my windows? There could be many answers to this question. Older windows are more susceptible to mold development because they are less efficient, and often don't seal as well as modern windows.
Leaks
Old windows can develop leaks, often due to lack of maintenance. These leaks can form around the windows and can get into drywall, which can cause mold development over time.
Condensation
Windows can develop condensation at times of year when it's cold outside and warm inside. Condensation forms on windows much like on glasses of iced tea in the summer.
If enough condensation forms, it may dribble down to the window frame, creating an environment where mold can easily develop. Mold on window from condensation can be difficult to control without controlling the condensation itself. The best way to stop mold growth from condensation is to eliminate the formation of condensation on the window.
Inadequate Ventilation
Poor ventilation caused by heavy drapes can lead to mold growth, especially when moisture is present. Poor ventilation holds moisture on the window, preventing it from drying.
How to Tell If There’s Mold on Your Windows
Know the signs that mold is growing on your windows. Being able to identify mold growth can help you stop the problem before it becomes serious. Mold can be several colors, including brown, black, and gray. Mold often grows in a circular formation and can dot your window sills in clusters.
Typically, mold growth starts small and gets larger over time. While it may be easy to remove in its early stages, it can get more difficult to remove with time.
How Does Mold Impact Your Home and Health?
Mold can negatively impact your home and health. The longer that mold is allowed to grow in your home, the more problems mold growth may incur.
Effect of Mold On Your Home
Mold breaks down organic matter, so when it grows, it can cause parts of your home to lose structural integrity. The mold that grows on wood beams, for example, can cause wood beams to become soft. Eventually, mold growth on wood beams can lead the wood to lose strength. Mold can also cause drywall to crumble with time.
Effect of Mold On Your Health
Mold is bad for your health in many ways. People allergic to mold may have severe reactions to breathing in mold spores or exposure to mold on their skin. Immune-compromised people may develop a lung infection, and people with asthma may experience asthma attacks when they breathe in mold.
How to Clean and Remove Mold from Windows
Cleaning and removing mold from windows is easy when you catch it in the early stages. Wear gloves and protective equipment when cleaning mold. If there is a lot of mold or mold that has spread beyond your home's window sills, call a professional cleaning/remediation company.
- Dry the window sill with a dry, clean rag.
- Spray the window sill with undiluted vinegar.
- Allow the vinegar to sit on the window sill for an hour.
- Remove the vinegar (and mold) from the sill with a clean, dry rag.
How to Prevent Mold from Growing on Your Windows
The best way to prevent mold from growing on your windows is to keep your windows clean and dry.
Improve airflow around your windows. Draw back your drapes during the day, and consider switching to cotton curtains to allow air to flow around your windows. Move furniture away from windows to allow for space to flow around furniture and windows.
Reduce condensation. Reduce humidity in rooms where condensation is often found on windows. Run vents and use dehumidifiers. Consider installing a whole-home dehumidifier if needed.
Consider new window installation. Old windows are more vulnerable to mold development because they are energy-inefficient and more prone to leaks. Modern windows seal tightly and can be made from condensation-resistant glass to reduce the chances of condensation forming on the glass. If you frequently notice mold growing on your home's window sills, it may be
time to replace your windows. Contact a window installer and dealer you trust to discuss window replacement.
When to Call a Professional for Mold on Windows
Don't wait to get help with mold. If you struggle to prevent mold development from forming on your windows, take action. The professionals at Woodland Windows and Doors can help with commercial and residential window replacement in the Chicago area.
We offer custom finishing and sell windows in a range of styles. Our energy-efficient windows and condensation-resistant glass can help you control moisture, humidity, and the temperature in your home. With new windows, you can make the environment in your home less vulnerable to mold development.
Our window replacement services are
efficient and worthwhile. Want to know more about how to improve your home's value and maintain a comfortable indoor environment? See our
guide to remodeling.
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