How to Prevent Window Fogging and Condensation

Condensation is caused by humid air coming in contact with a cold surface, such as glass. Just like a glass of ice water in warm room, condensation creates many small droplets of water, and becomes visible on the glass surface. This is completely normal, and will occur in every home at one time or another. Everything in your home that involves water will contribute to excess humidity, such as showers, mopping, watering plants, and heating/air conditioning units.

Excessive condensation however, may be linked to a problem with the window, such as:

• Cracked, chipped, or peeling paint
• A drafty window seal
• Gaps in between glass and window frames, allowing excess airflow
• Cracks or chips in window glass
• Excess water within the home

Although condensation is not completely preventable, there are several methods that can help reduce the problem.

• Ensure that all outside ventilation sources are open and flowing.
• Open windows and doors to "air out" your home, allowing moist air to exit and dry air to enter.
• Purchase a humidifier. If you have one, check the settings to make sure it is working properly.
• Open fireplace vents to allow moist air to escape through the chimney.
• Keep indoor plants watered, but do not over saturate, as it can build up moisture in the home.

The following chart shows the recommended humidity levels during winter seasons, and you can measure your indoor humidity with a humidistat or psychrometer.

It is also important to remember that sometimes you will see an increase in humidity after you’ve installed new replacement windows. This is because the seals in your old windows were cracked and drafty, allowing air (and therefore moisture) to escape from your home. Your new windows however, have tighter seals, and are allowing less air to escape outside.