The process of conversion of a substance from its gaseous state to its liquid state due to cooling, is termed as condensation. When water vapor or moisture present in the air, comes in contact with a cool surface, it gets converted into droplets of water.
Condensation takes place when the temperature of the surface is equal to, or less than, the critical temperature for condensation of water, which is known as the dew point. Now, let us see what is the reason behind this phenomenon.
During winter, the temperature inside the house is higher than the outside. In such a scenario, the air inside the house is warm and warm air has the capacity to hold more moisture as compared to cool air.
There are several factors that contribute to the moisture content or humidity indoors, which include use of showers, steam released during cooking, and respiration by humans, indoor plants and pets, among others. All this accumulating moisture is unable to escape and causes increased moisture content in the air within the house.
When this humid air comes in contact with the surface of the windows that have a lower temperature, heat transfer by conduction takes place and there is a fall in the temperature of air. As soon as the air gets cooled, it is no longer able to hold the excess moisture which is released in the form of droplets of water.
What Causes Condensation in Double Pane Windows
This phenomenon, which appears as a foggy layer, is common in case of single pane windows because of the reason that these windows get cooled down to the outside temperature. However, double pane windows have an advantage as these have a insulating layer of a gas, such as argon, sealed between the two panes.
A double pane window is a window having two panes with a spacer between the two. The spacer separates the two layers and is usually made of a substance that is a poor conductor of heat. A gas with very low conductivity, such as argon, is used to fill the space between the double panes.
Sometimes, a vacuum may also be created between the two panes of the window, to ensure almost negligible conduction of heat. The substance used as spacer also contains a desiccant such as silica gel that absorbs any amount of moisture that might have got accumulated between the two panes during the process of manufacturing.
Not only this, the silica gel absorbs any amount of moisture that may accidentally enter the space between the panes, thus preventing fogging of the surfaces. However, once the silica gel gets saturated, it is necessary to get it replaced. But why do the seals of double pane windows get damaged over time? Here's an answer to this question.
As stated earlier, double pane windows have two layers of glass with gas between them. Now, during the day, the increase in temperature causes expansion of the gas, which in turn forces the glass on both sides to expand as well. At night, however, the atmospheric temperature falls and this results in contraction of the glass.
This constant expansion and contraction takes its toll on the seal which gets worn out over time. Once the seal is worn out, the window ceases to perform its function and has to be repaired or replaced.
The process of repairing double pane windows with condensation, is relatively new, and is termed as defogging. This process consists of 3 steps and begins with the drilling of a hole in the window through which a liquid cleaner is sprayed inside. A vacuum pump is used to remove the moisture completely and a defogger is then permanently fixed to the window.
Nevertheless, it is important to note that the process of defogging double pane windows, though effective, does not solve the problem completely. This is because the seal, if damaged, remains as such. Condensation, if neglected, can cause permanent damage to double pane windows.
Condensation is not the only indicator of a faulty window, or a damaged window seal. In regions that do not experience extremes of temperature or in houses that have relatively low humidity, it is difficult to spot a faulty window. This is the reason why you need to get your windows checked by professionals at regular intervals.
Nowadays, technologies such as infra-red cameras have made things easier. All you need to do is take images of the windows using such cameras and analyze them.
Since the cameras are sensitive to temperature, you can easily make out as to what extent your windows are really insulating your house from the outside temperature. For example, presence of red color indicates a higher temperature while bluish tones indicate lower temperatures.
Thus, in case you detect even mild condensation in your double pane windows, you should immediately take steps to deal with it. Although getting it repaired is an option, you should straightaway replace your window with a new one, should the problem persist.