Condensation on Windows

Remember putting a pot of water on ra­diators to add humidity to the air in win­ter? This was a common practice in the days when homes were built with wood board sheathing and sometimes no insu­lation.  Today, builders use panel prod­ucts for sheathing, and walls and ceilings that are insulated. Houses are "tight" and prone to moisture problems rather than difficulties with dryness.  This also includes windows.

The presence of condensation on a window indicates more than just higher humidity. It's a signal that the home's indoor temperature may be too high and not ideal for creating a comfortable environment. Take a closer look at the window – without fail, when droplets form here, it might be sending out an SOS regarding the temperature balance inside your house!


Understanding Window Condensation

  • Condensation can form on interior glass surfaces when too much moisture is in the air. If the interior of a structure exceeds certain limits of water in the air, the moisture will condense and show up on comparatively cooler surfaces, such as glass.

    Windows are typically the coolest areas of interior walls, even if they have storm panels, are glazed with welded insulating glass, have Low-E insulating glass, or use triple pane glass. When the warm, room-temperature air comes in contact with the glass surface, the air is cooled, and if there is enough moisture in the air, the dew point will be reached, and the water in the air will condense. A 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 glass's cooler surface causes condensation. Recommended humidity levels in winter months should not exceed 30-35%. If these humidity levels are exceeded, you may want to take measures to reduce the interior humidity level, such as:

  • Checking your ventilation
  • Using a dehumidifier
  • Turning the humidifier on your furnace down (or off)
  • Making sure blinds or curtains are open during the day
  • Leaving ceiling fans on to promote air movement
  • Use an exhaust fan in bathroom areas when showering


Prevention is the Key

With a better understanding of window condensation, you can be well equipped to tackle any problem you have with condensation on your windows. As long as prevention and maintenance guidelines are followed, it is possible to mitigate the effects of condensation on windows. With the right education and preventative measures, dealing with pesky window condensation doesn’t have to be difficult.