An example of this is when a bathroom mirror “steams up” after a hot shower. Just like that mirror, the inside or outside of your window can sweat or fog because of temperature differentials. Another good analogy is when you have an iced drink on a warm summer day, and the glass has moisture on the outside of it. The warmer air meeting the cooler surface of the glass causes condensation to form.
Moisture in the air within the home is often the culprit. Condensation occurs on inside window surfaces whenever surface temperature falls below the dew-point temperature of the room. The window, therefore, determines the practical limit of humidity for the space in winter, and condensation may appear on the glass, frame, or sash, depending on relative thermal characteristics of these components.
Excessive humidity is the cause of most window condensation. As the outside temperature drops, the window glass temperature also drops. When moist air comes in contact with the cold glass pane, the moisture condenses and forms water droplets. Determining when the condensation will occur and preventing it depends on the energy efficiency of the window, the relative indoor humidity of the home, and the exterior and interior temperature.
There are primarily three causes for temporary window condensation.
New Construction: Wood, plaster, cement and other building materials used in new construction and remodeling produce a great deal of moisture. When the heating season starts, this moisture will gradually flow out into the air in the home. It will usually disappear during the first heating season and not cause any further trouble.
Heating Season: At the beginning of the heating season, there may be a certain amount of temporary condensation. During the humid summer months, your house can absorb some moisture. After the first few weeks of heating, this moisture should dissipate.
Preceding Temperature Shifts: Sharp, quick drops in temperature can also create temporary condensation problems during the heating season.
It seems natural to blame the windows but they do not cause condensation. Window condensation is really an indication of excess humidity and moisture in your home. The glass simply provides a surface on which the moisture condenses visibly. It is usually the first place you notice condensation because glass surfaces have the lowest temperature of any surface in a house. The insulation and construction materials used today are designed to keep cold air outside. This is especially true of new windows. While energy-efficient designs and weather-stripping keep cold air outside, they also keep warm moist air inside. Older window designs were less efficient and consequently allow moisture to escape.
The important thing to realize is that if excessive humidity is causing window condensation, it will also be causing other problems – sometimes hidden problems – elsewhere in your home such as peeling paint, rotting wood, buckling floors, deteriorating insulation, mildew or moisture spots on your walls and ceilings.
To prevent condensation on windows, you’ll have to be proactive in stopping the accumulation of moisture in your home. Read the following tips to learn how to reduce condensation on windows.
Window condensation should only occur when there are extreme temperature differences between indoor and outdoor spaces. In addition, there should only be a fairly small amount of water on the glass. Condensation will be seen on the inside of a window during winter months, and will present itself on the outside of a window during summer months.
If you find condensation between the two layers of glass in an insulated window, the airtight seal has probably failed and the glass unit will need to be replaced.
If there is too much moisture inside the home, you will see evidence during both the cold and warm seasons. Moisture spots on the ceiling or walls, peeling paint, rotting wood, delaminating plywood, moisture on exterior walls, and fungus, mold or mildew growth are signs of a more serious moisture problem. Should you experience these symptoms, an expert heating & cooling contractor should be contacted in order to solve the problem.