What Causes Condensation – Exterior Condensation


Why do I have condensation on my windows? What causes condensation on windows? How do you stop condensation?  These are all questions that get asked, especially around the end of fall and the beginning of winter as the temperature drops significantly and people notice the environmental changes and sometimes the appearance of moisture on their windows. This article focuses on exterior condensation and it’s causes.

First of all establish where the condensation is occurring – it is on the inside or the outside? The best way to determine this is to take a towel and dab it on the glass surfaces. If it isn’t wet from the inside or the outside the condensation may be between the glass panes, in which case it could be a sign of seal failure on your glass unit.  If this is the case the insulated glass unit would need to be switched for a new one – call your contractor or dealer to arrange a replacement unit through your Climate Solutions warranty, as all glass units come with a lifetime warranty against seal failure.

If the condensation is on the outside of the window it is usually a good sign, often occurring during the summer months.  If there is high humidity, a clear night sky or no wind it can cause exterior condensation.   It shows that the house is keeping out the heat and retaining a cool temperature inside.

There are many environmental factors that can affect exterior condensation – such as the angle of the sun, the outside humidity and the temperature.  Very simply, if the humidity outside reaches the dew-point (the point at which moisture in the air is converted into water) then you will get condensation, regardless of the windows you have.

Problem condensation is repeated condensation that can lead to health problems and dirty vinyl windows – this would be if the condensation doesn’t disappear or if it is elsewhere in your home, such as the walls, but this won’t happen with exterior condensation.
Finally, from the Better Business Bureau:
“Condensation is visible evidence of excessive moisture in the air. It may appear as water, frost, or ice on the room surface of windows and doors….you must remember: Windows do not cause condensation. Therefore, windows cannot cure condensation”

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