6 Facts About Window Condensation That You Must Know

Foggy windows are a common issue in many homes, especially during winter cold snaps. Some homeowners think it's caused by defective windows or poor installation. If you're a diligent builder, however, you'll know only too well that's not the case. 

1. Window condensation is caused by excess humidity.

When a house has high levels of humidity, water vapor in the air tries to find a way out. Because modern buildings are designed to be air-tight and keep the cold out, they also trap moisture inside. So, when the vapor comes in contact with glass windows that are cooled from the outside, it condenses into drops of water. The moisture that forms on the glass is condensation.

2. Family lifestyle affects humidity levels.

There are activities being performed every day around the house that generate moisture. These, in turn, increase humidity levels. Examples include cooking, showering or bathing, and washing clothes. You'll often find that houses in the same location and built the same way have different humidity levels.

Keep in mind what household activities occur in a home. If you know you're dealing with a family of six, then expect the daily hustle and bustle to encourage the generation of moisture, and thus high humidity in the house.

3. An uncontrolled indoor temperature promotes interior condensation.

Condensation on the interior side of the window glass is most likely due to high indoor humidity. This can be prevented by striking a balance between the indoor and outdoor temperatures. As the outside temperature drops, a high interior humidity level will produce condensation. 

You can avoid issues like this by installing dual-paned, insulating glass (IG) units that do not easily fog up in high humidity. A Low-E coating on the glass will also reduce heat loss and block UV rays. Placing vents and exhaust fans in humid rooms like the kitchen and bathroom will improve air circulation and reduce moisture levels. A humidistat in living spaces is beneficial as well.

4. Outdoor environmental conditions cause exterior condensation.

Window glass that is cooler than the outside air will create condensation on the exterior side of the glass. This will evaporate as the glass warms up. Good air circulation outside the window will also help the water vaporize faster. 

Survey the surrounding areas directly outside the windows and around the rest of the house. Shrubbery, trees, and structures can limit the amount of air that circulates throughout the vicinity of the house. Knowing the typical weather conditions in the region will also help you predict the possibility of exterior condensation. 

5. Different types of windows will be affected by condensation differently.

All window types are prone to condensation. Nevertheless, they have particular ways of responding to moisture. When identifying how you can minimize potential damage from condensation, know your options for window materials:

  • Wooden windows should be properly finished or painted. Wood is porous, so moisture can easily seep into and through the material.
  • Vinyl windows are outfitted with a "weep" system that drains water out. They will be fine as long as the drainage holes are not blocked with dirt.
  • Aluminium windows are very susceptible to condensation because they transfer heat. The aluminium frame quickly becomes colder than the surrounding air.

6. Condensation can be costly and dangerous.

Excess moisture on windows can cause costly problems to a house in the form of decaying wood, peeling paint, and buckling floors. Health hazards like mold and mildew growth might also present themselves.

Always remember that prevention is better than cure!


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