Window Condensation Management

My windows have condensation on them. Are they defective?

If you are troubled during the fall and winter by condensation on the windows of your home, you aren’t alone. Window condensation is a common problem in cold climates. Understanding what causes the condensation is the first step in solving the problem. If you are experiencing condensation on the surface of your windows they are not defective but conditions may have been unintentionally created that caused a “dew point.” Simply put the dew point is the temperature at which the water vapor in the air becomes saturated and condensation begins on solid surfaces.

Why does the condensation collect on my windows, but not on my walls?

The fast answer is because humidity cannot pass through the material glass while it does pass through sheetrock, wood, siding and even sheet plastic. Also your walls are constructed in our area to be 4 or 6 inches thick while the insulating space in your glass is only 5/8 inches thick making glass a very inefficient insulator.

What are some ways to reduce the interior humidity level?

There are several ways in which you can help reduce the interior humidity in your home; they include checking your ventilation, using a dehumidifier, opening blinds and curtians during the day, leaving ceiling fans on, and using an exhaust fan in the bathroom. 

If glass is a poor insulator, then why are my windows not completely covered in condensation?

Your recent ancestors grew up in houses with single pane glass. If it is zero degrees outside and 70 degrees inside, the inside surface temperature of the glass is only 14 degrees! It was typical not only for condensation to form on the glass, but also for the window to be covered with frost.

Then glass manufacturers started using double pane glass with a space in the middle of the two panes calling it “insulated glass.” Research indicated that a space of 5/8 of an inch was the perfect air gap. More than 5/8 inch and the air would begin to move inside the gap because warm air rises, thus reducing the insulating value. In later years, glass companies began developing films on the glass that increased efficiency by reflecting the heat back to its source. Argon gas was added in-between the panes to achieve maximum thermal benefit. With these improvements, you can take the same 0 degrees outside and 70 degrees inside and have an inside glass surface temperature of about 56 degrees. This significant improvement however is still no match for sub-zero temperatures outside and high humidity inside.

Watch a video on understanding condensation:

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