Home Garden

Low-E Argon-Filled Windows That Mildew

Mildew on your low-e, argon-filled window is not usually an indication that the window’s seals have failed. Low-e glass contains a thin layer of metallic oxide that reduces the loss of heat through your windows. Argon is an odorless, tasteless gas that is used to replace the air inside your window and helps prevent heat loss as well. This does not, however, completely eliminate moisture that is transferred through the window, which can lead to mildew growth.
  1. Condensation

    • Most windows leak air and moisture because of a process called air and water infiltration. This is because windows are made with weep holes to allow water caused by condensation to leak to the exterior. Excess humidity in your home caused by the normal operation of washing machines, heating appliances and showers, or due to humid weather conditions, will cause your windows to collect condensation, which occurs first on windows because they have a lower temperature than other interior surfaces. In homes with a lot of moisture present in the air, it is not uncommon for the windows to be moist most of the time, which can lead to mildew growth.


    • Condensation on your low-e, argon-filled window does not usually indicate a failure in the windows. While these types of windows are more resistant to mildew growth and moisture, they are not completely impervious to it. Before calling the manufacturer, consider the humidity levels in your home. If these are normal, then contact the manufacturer to determine if the window needs replacing. Most manufacturers provide warrantees which include inspection and replacement in the event of seal failure.

    Mildew Removal

    • Mildew is typically brown to black, often resembling dirt or dust. It is a fungus that commonly grows in a consistently moist environment. A faint discoloration of your window frame may also be water stains, not mildew. To clean mildew from interior window surfaces, mix a solution of one cup bleach and one gallon of water. Dampen a sponge with the solution and wipe the stains away. Test a hidden area of the window frame first, to make sure the bleach won’t damage the finish. Wood frames and some sealants may require refinishing after using bleach. If the bleach cannot be used, use vinegar in its place. However, vinegar may not remove heavy staining.

    Controlling Humidity to Prevent Mildew

    • To eliminate mildew growth, you first have to address the humidity in your home. Any appliance or activity that uses water will put moisture into the air and increase your home’s relative humidity. To reduce your home’s humidity doesn’t mean stopping this activity, but rather eliminating moisture that doesn’t need to be there. Fix leaking faucets and empty containers that contain standing water such as sinks and appliance drain pans; cover fish tanks, too. Close your toilet lids and install exhaust fans in kitchens and bathrooms. Run dehumidifiers to help remove moisture from basements and crawl spaces and ensure that your home has adequate ventilation as well. Doors and windows shouldn’t be so air-tight that air cannot circulate from the rooms. Drying your floors after mopping and drying your clothes outdoors when possible also help reduce excess moisture. Cleaning your window at least once each month, both inside and out, can prevent growth of mildew and staining.