All About Window Condensation: When Is It a Problem?

Jan 30, 2020

Whether your house has older windows or brand-new ones, condensation may develop on your window glass from time to time. When you see this condensation, you may wonder if it signals a window problem. While most window condensation is no cause for alarm, one type of condensation does signal a window problem. 

Learn about the three main types of window condensation and when this condensation signals a window problem.

Interior Window Condensation

Interior window condensation is very common and no cause for alarm. This condensation develops when warm, moist indoor air comes into contact with a cold window. Since warm air can hold more moisture than cold air, warm air deposits the moisture it holds onto on a cold pane of glass as soon as the glass cools the air. Not surprisingly, more interior condensation develops when the humidity level in your home is high. 

If you just installed new windows and they develop more interior condensation than your old windows, then this is actually a sign that your new windows have a more airtight seal than your old ones. When windows have leaky seals, warm, moist indoor air can escape through these seals before it comes into contact with the cold window and deposits moisture onto it.

While interior window condensation does not signal a window problem, if excessive amounts of condensation develop, it can drip onto window frames, window sills, and interior walls, potentially leading to moisture damage of these items.

If you have vinyl or fiberglass window frames, then this moisture is unlikely to damage these frames. However, wooden frames can be damaged by excessive moisture. To prevent wooden frame moisture damage, coat your wooden frames with a waterproof sealer and reapply this sealer on the schedule your window installation expert recommends.

Small amounts of interior window condensation that appear on occasion typically do not cause any home damage. Allow this condensation to evaporate or simply wipe it off with a cloth, if desired. 

However, if you are plagued with an excessive window condensation problem, then take steps to keep indoor air drier to prevent home moisture damage. Run home exhaust fans whenever you create steam in your home, and, if necessary, use indoor dehumidifiers to further control indoor humidity.

Exterior Window Condensation

Exterior window condensation is also normal and does not signal a window problem. Exterior condensation develops when outside air is warmer and more humid than cool indoor air. When you notice exterior window condensation, simply ignore it and let it evaporate, or, if it bothers you, wipe it off the window surface. 

If you have wooden window frames, be sure to protect them from all outdoor moisture by applying a waterproof wood sealer to them as well.

Condensation Between Two Window Panes

Unlike interior and exterior window condensation, condensation that develops between the two panes of glass in a double-pane window does usually signal a window problem. This condensation develops when warm moist air becomes trapped between the two panes of glass and then deposits moisture onto the interior side of either window pane.

Double-pane windows should be so tightly sealed that outside air cannot penetrate through the seals and into the space between the glass panes.

While this condensation may not pose an immediate hazard, this is usually a sign of window seal failure. When a dual-pane window seal fails, the window loses some of its insulative value as the insulative argon gas that lies between the two window panes is replaced with typical air. In addition, a bad window seal can lead to a window draft.

To fix this problem, replace the entire window unit with a new unit. While some windows can be resealed, you cannot reseal a window that has moisture between the two panes of glass, because the moisture between the glass cannot be removed before the window is resealed. 

If you have noticed condensation on your home windows, then use this guide to determine if your window’s condensation signals a window problem or not. Contact the window professionals at 1st Choice Windows & Siding to discuss all of your window needs today.