What causes condensation on double glazed windows?

Written by horacio garcia | 13/05/2017
What causes condensation on double glazed windows?
Condensation can build up between the glass on double-glazed windows. (window image by Marek Kosmal from Fotolia.com)

Window condensation is an especially difficult problem to solve with double-glazed windows. When moisture builds up between the inside pane and outside pain, it cannot be cleaned by conventional methods such as window cleaner and paper towels. The homeowner should be aware of what causes this condensation in double-glazed windows.


The most common cause of condensation on double-glazed windows is humidity. The outside window is colder than the inside window causing fog or frost to build up in-between the two panes. The window and house is extremely airtight and cannot breath. This tight condition will keep the utilities at a reasonable price each month, but cause damage over time. The moisture in the home is caused by cooking, doing laundry or just breathing and flows to the outside through plaster walls and wood of the home construction. Glass, however, does not allow moisture to flow through it. Ventilating the home will allow the moisture to escape the house freely and not cause a build up between the glass panes.

Window Coverings

Most people put curtains or blinds over the windows to gain privacy. During changing climate conditions, covering the window can keep the window panes colder than they should be causing a moisture build-up between the double-glazed windows. Condensation will begin to develop unless the homeowner opens the curtains and blinds in order for the sun to flow freely through the glass panes.


The thermostat setting in the home can cause condensation to build up between the double-glazed windows. If the thermostat is reduced dramatically at night in order to save energy, this will cause humidity to increase inside the home. This humidity increase will cause fog or frost on the inside of the window panes. It does not matter if the air-conditioning or heating unit is being used, what matters is the dramatic change in thermostat settings inside the home compared to the outside temperature. Keeping a constant thermostat setting will alleviate this problem.

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