How to Combat Condensation on Windowsills

Condensation may cause mold and mildew to grow on a windowsill.

Condensation occurs when warm air, which holds more water vapor than cold air, comes into contact with a cold surface. Thus, condensation commonly occurs on windows and windowsills, which are generally the coldest surfaces in the home. Condensation on windowsills can cause serious damage, including peeling paint and rotting wood. Fortunately, you can combat condensation on windowsills.

Instructions

1. Run a dehumidifier. Dehumidifiers are designed to remove moisture from the air and the surfaces, including windowsills. Many new humidifiers come with a humidistat and an automatic shut-off.

2. Fix window cracks. A crack allows cold air to enter, resulting in condensation.

3. Replace the window with glass that has a higher condensation resistance rating. The National Fenestration Rating Council determines the CR rating, which ranges from 0 to 100. The higher the rating, the better the glass is at preventing condensation. This, in turn, means less water dripping onto the windowsill.

4. Heat the area near the windowsill. Baseboard heaters under the windowsill can help prevent condensation. Space heaters may also be effective.

5. Reduce moisture-generating activities inside the home. Such activities include taking long showers with hot water, cooking without lids and drying clothes with a dryer that does not vent to the outside.

Tips & Warnings

• Mildew-resistant paint should not be applied to windowsills, because these paints can harm children, if ingested.

References

• Cornell University: Moisture Condensation at the Windows
• Enlighten: Preventing Condensation on Windows
• University of Missouri: How to Prevent and Remove Mildew - Home Methods