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How to Prevent Condensation Build Up on Double Glazed Windows

We’ve all experienced the problem of condensation build up on double glazed windows. Double glazed (or double paned) windows contain a layer of air or gas trapped between two panes of glass. While this can slow down heat transfer between the two sides of the window (keeping heat inside during the winter and outside during the summer) it can also allow condensation to build up between the two panes of glass, out of the reach of paper towels or cleaners. While this is a frustrating problem, there are several steps you can take to avoid or minimize the issue.

First, Identify the Cause

Condensation build up on double glazed windows is usually caused by humidity in the air inside your home. When moisture-laden air comes into contact with a cooler surface (such as your windows) the moisture condenses out of the air and clings to the glass, much like what happens to the glass around an ice cold beverage. When it comes to your double glazed windows, this phenomenon is usually noticeably worse during the winter, because the glass in the windowpanes is at a much lower temperature than the air inside your home. Because the outside pane of glass in double-glazed windows is colder than the interior pane of glass, any moisture in the air will tend to bead up between the two panes, where it is out of your reach.

This humidity inside your home can be caused by many factors. Running a clothes dryer can drastically increase indoor humidity (think about where all that water that leaves your clothes is going!) as can showers and other sources of running water. Even something as innocuous as a freshly painted room can noticeably increase humidity levels. As the paint dries, the moisture leaves the walls and enters the air in the room.

Solutions and Quick Fixes

Depending on the severity of the problem, there are several possible solutions to reduce the humidity inside your home and prevent condensation build up on your double glazed windows. One of the easiest options is to run a dehumidifier in the affected rooms. In order to keep energy costs under control, this option is best for temporary situations such as while fresh paint or plaster is drying. If humidity in an area of your house is an ongoing problem, you might want to consider a more permanent solution to reduce moisture in the air.

Leaving doors open inside your home can help to keep air circulating throughout the house, and can prevent any one room from becoming too humid. Make sure after showering or running a clothes dryer to keep the bathroom or laundry room door open until the air in the room no longer feels humid. If you have one, running the exhaust fan in the bathroom after showering will reduce moisture in the air considerably. Running portable fans in humid rooms can also help to keep air circulating, provided the door is left open.

Finally, keeping the area near any double glazed windows relatively warm will help to prevent condensation build-up by keeping the glass warm enough that moisture from the air will not condense onto it.


If reducing the overall humidity levels in your home has not prevented condensation build up on your double glazed windows, you may need to investigate further causes of the problem. Any cracks in the windows could be allowing cold air from the outside to seep between the windowpanes, decreasing the surface temperature of the glass and making condensation more likely. Unfortunately, these cracks may need to be addressed by a professional, or the window may need to be replaced.

If you do opt to have your double glazed windows replaced, or if you are buying them for the first time, it is important to keep in mind that newer models may come pre-fitted with trickle vents. Trickle vents allow a small flow of air to pass between the windowpanes, which can help to keep condensation in check.


Double glazed windows can be an energy efficient way to prevent heat loss to the outdoors in winter, and heat entry into the house in summer. Keeping them free of condensation can be a challenge, but staying mindful of indoor humidity levels can reduce or even prevent condensation build up.


For a more scientific overview of condensation on double glazed windows:

For general tips