There are many causes of foggy windows of which some are linked to the window’s quality and lifespan but also to the indoor environment. If you want to learn more about what causes on window condensation, here is a list of the 8 probable scenarios:

Temperature variations – The least dangerous cause of foggy windows is simply temperature variation. When cold surfaces suddenly get in contact with warm air, tiny water droplets form on them. This is the case with exterior condensation early in the morning and interior condensation on windows in winter.

Old windows – Every window has a lifespan, depending on its materials and quality. Once the window passes its life expectancy, it will start losing functionality. Besides condensation, it might also become loose and drafty. In these cases, the condensation happens inside, not on the exterior window glass.

New windows – An opposite scenario to the previous one is condensation on new windows. Don’t worry though, this is completely normal. New windows have very strong and tight insulation, especially in the first year.

Poor window installation – whether new or old, if your windows are not installed properly, they will not provide good airflow and temperature balance. Condensation can happen if the window is too small for the opening or simply doesn’t align with its shape. Here, we recommend a replacement or reinstallation.

Old Caulking  – Window thermal sealants break with time. This will cause condensation between the glass panes which with time, will lead to mineral buildups too. If you notice that the sealant is damaged, consult with professionals since replacing the caulking might not be enough to stop this issue.

Pressure – If you have condensation between window panes, you might be dealing with a leaky gas. The gas between the panes leaks over time, approximately 1% per year. However, if something puts pressure on it, it might increase this percentage and even cause a sudden crack in the panes.

High humidity levels – The number one cause of windows fogging up in the house is high indoor humidity. You can especially notice this after taking a shower or cooking. High humidity is also present in homes with poor ventilation and insulation. Sometimes even a clogged pipe or a broken sump pump can increase your humidity levels and cause window condensation.

Plants – Plants breathe just like humans do. If you are a plant collector and enthusiast and have over 40 plants inside, they might be the reason for your window condensation. However, don’t throw them in the bin. Simply place them closer to windows and open up the windows more often to increase airflow.

condensation on window Calfeutrage Apex caulking


Now that we have gone through the 8 primary causes of condensation, it’s time to talk about solutions! You should choose the solution based on the reason your windows are fogging up. Before you decide, make sure you think things thoroughly and consult with experts.

Dehumidifiers – If the cause of condensation in high-humidity, the best solution is using dehumidifiers. For those wondering how to keep windows from fogging up when raining, dehumidifiers are the perfect solution. They will eliminate your indoor condensation if the cause is high humidity and temperature variations.

Smart thermostats – Besides purchasing dehumidifiers, you can also try to manage your humidifier, adjusting the indoor temperatures based on the weather outside. Smart thermostats will help you achieve just the right temperature balance. You can set your preferred temperatures even before it rains.

Storm windows – For reducing condensation on windows in fall or winter, we recommend adding storm windows. They will warm up your regular window, which will reduce the temperature difference between the indoor air and glass surface. Storm windows will also cut your energy spending as they provide extra insulation.

Upgrade ventilation – Another way to keep control of indoor air temperatures is by upgrading your ventilation system. Schedule cleaning and repairs to allow proper airflow in the house. You can boost ventilation by installing new vents in moist spots like kitchens, bathrooms, and basements.

Window replacement – Sometimes the issue is larger than poor ventilation. If you frequently say “why does only one window have condensation” or “my windows are dripping with condensation, I don’t know what to do” you need a bigger change. Window replacement is a-must in homes with severe condensation issues. When choosing new windows, focus on the quality, material, and window type.

Glass replacement – If condensation occurs between the glass panes, opt for window replacement. Consult with your local window contractor to see whether you need a full or partial replacement. in some cases, homeowners only need to upgrade their glass and keep their old frames and sash.

Weatherstripping – A quick and simple solution, weatherstripping will help you keep warm air inside. This will increase the window’s temperature as well and therefore reduce condensation.

We especially recommend weather stripping for those using storm windows and during colder months. Just like storm windows, weather strips also increase energy efficiency.

Window Caulking- Window caulking helps to insulate your window and prevent cold or warm air and water from infiltrating your home. While caulking may help to reduce condensation, it is not guaranteed that it will stop condensation and fog from appearing on your window.

Use your windows – Our last tip for reducing condensation might sound simple, but homeowners forget it regularly. If your house is damp, simply open up your windows and allow air to circulate. For homes with moisture issues or many plants, we recommend opening up the windows at least 3 times per day.