Why Are My Windows Wet?

| November 9, 2011 | 0 Comments

You didn’t have this problem in the summer, but now it’s finally fall. Mother Nature’s not teasing any more. The days are cooler and the mornings are a bit chilly. And every morning you look outside to see what the day’s going to bring and the windows are wet or fogged over.

What your seeing is condensation. It can happen not only in your home but in commercial buildings as well.

We’ve collected 9 questions and answers about condensation to give you some answers about why your windows are wet on the inside.

1. What is condensation? Moisture on the windows is a form of condensation we are all familiar with. So is the water that forms on the outside of a glass of iced tea in the summer. It comes from water vapor in the air. It can appear on the interior or exterior of window, wall, ceilings, and other areas.

2. What causes condensation? When warm, moist air comes into contact with cooler surfaces, the excess moisture in the air condenses. That’s because the cooled air next to the cool surface can’t hold as much moisture as the warmer surrounding air.

3. What does the condensation on windows, walls, and ceilings mean? The best way to think of these indicators is as a warning sign. It may mean that excessive indoor moisture (high humidity levels) could be doing unseen damage to other parts of your building.

4. What is humidity? Humidity is water vapor, or moisture, in the air. Usually it’s invisible. In the form of steam or ground fog, enough has condensed to be seen. All air contains a certain amount of moisture, visible or not.

5. What is relative humidity? Air can hold only a limited amount of water vapor, and that amount depends on the air temperature. When air at a certain temperature contains all the vapor it can hold, it’s said to have a relative humidity of 100%. Thus, when it holds only half as much water as it could, the relative humidity is 50%. Cooler air can hold less vapor than warmer air. So air at 30°F and 100% relative humidity contains less water than air at 70°F and 100% relative humidity.

6. Can relative humidity affect my health? Most experts agree that relative humidity can affect your health. They suggest maintaining indoor humidity levels between 30% and 50%. According to the World Health Organization, at levels higher than 65%, upper respiratory illness might occur in people suffering from asthma and allergies. Mold and mildew growth also occurs with higher moisture levels.

7. What does excess humidity do to my home or building? Excess humidity contributes to the deterioration of any building. It can pass through walls and freeze in the insulation. In spring it melts, damaging your ceiling and walls. Or, excess humidity can force its way out through siding to form blisters under exterior surfaces. Excessive relative humidity levels may also lead to higher levels of unwanted mold and mildew growth.

8. How does moisture go through walls & ceilings? Moisture in wet air tries to flow toward dry air. This is due to “vapor pressure.” The flow acts independently of air currents. In winter, inside air is much more humid than colder outside air. So the vapor pressure, or equalization process, can actually force inside moisture through cement, wood, plaster and brick. Some varnishes and paints block the flow of the moisture, so condensation can occur between the inside and outside walls, or under exterior paint surfaces. This can cause rot in a buildings wood components, blistering in paint, and deterioration of other building materials.

9. Does condensation occur only in winter? No. Although condensation is most common in winter, it can occur whenever water vapor in the air comes in contact with a surface temperature lower than the dew point (the temperature at which air becomes saturated and produces dew).

 Bonus Question & Answer: How can you correct it? The easiest way is to reduce the amount of moisture in your home or building. But sometimes its not as easy as it sounds. There are a lot of ways that moisture can invade your space.

Filed Under: Moisture

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