Why Do My Windows Fog Up?
If one or more windows in your home occasionally resemble a cold pitcher of iced tea sweating on a hot summer day, you have a condensation problem. Window condensation is often irritating – and if ignored for too long, it can cause serious damage, particularly if you have older windows.
While condensation buildup can cause visible problems such as rotting wooden molding and window frames, it can also damage the interior plaster around the windows. In severe cases, the moisture can seep into the walls, causing the growth of mold and compromising the structural integrity of your home.
What causes your windows to fog up?
Condensation on the inside surfaces of windows most often occurs in the winter, when warm, moist air inside your home condenses on cold windows. Exterior condensation is commonly caused by rain or dew that collects on the window surface when the window is colder than the dew point. If there is too much moisture inside your home, you may even find evidence during both the cold and warm seasons.
Condensation can form on any type of windows – from single pane windows that are or aren’t protected by storm windows to more advanced double- or triple-pane insulated glass units (IGUs). In multi-paned windows, condensation begins to form when the seal between the panes cracks or becomes overly worn, allowing moisture in the air to settle inside. In addition, the moisture-absorbing desiccant material between glass panes can become saturated with water, causing serious damage to the window, frame and sash.
Have your windows inspected
If you find condensation between the two layers of glass in an insulated window, the airtight seal is broken and the glass or window may need to be repaired or replaced. If you have single pane windows, adding securely-fitted storm windows may put an end to condensation buildup. A glass installation professional will be able to inspect your windows and advise you on the best course of action.
In serious cases, you may have to replace the entire window. This may be a good idea if the windows are old or damaged by moisture. If replacement windows are needed, consider choosing IGUs with an argon or krypton gas fill that will provide better insulation value while reducing convection between the panes.
Reducing indoor humidity
When the air in your home is warmed, either by your heating system or by the weather, it expands, allowing it to hold more moisture. As it cools down, it contracts until it reaches its saturation point; at this point it releases this excess water in the form of condensation.
Common household activities, including showering and bathing, cooking, using unvented gas heat or even breathing, release moisture into the air. On cold days, window glass is chilled by the cold air outdoors so it is at a much lower temperature than the heated, moisture-laden air inside your home. When the warm indoor air contacts the cold glass, its temperature is immediately lowered so that it can no longer hold as much moisture vapor as it did. As a result, the excess moisture condenses on the cold glass to form the drops of water that you see.
There are additional factors that affect condensation, including the number of windows in your home, what type of heating system you have, the insulation and vapor barrier in your home and even the type of soil and degree of drainage in the yard surrounding your house. To help reduce this problem, we have a few suggestions that might help:
- If you operate a humidifier on a regular basis – including a unit that works with your heating system – turning it down to a lower setting will release less moisture into the air.
- If certain areas of your home tend to be more humid or damp than others, you may consider investing in a disposable moisture elimination product that can be hung up or placed unobtrusively in the affected area. These products are usually self-contained and are easily disposed of when the desiccant has absorbed its limit.
- Use your exhaust fans every time you cook or shower. Both activities release a lot of moisture into the air, which doesn’t dissipate quickly. Allowing the fans to run for up to 20 minutes after cooking or showering will greatly help reduce moisture in the air.
- Good air circulation can also help reduce condensation buildup on windows. Using ceiling fans in the winter will not only help reduce moisture in the air at window level, it will move warm near the ceiling down toward the floor, which will help keep the rooms comfortable.
- Cracking or opening a window – weather permitting – can release some of the moist air trapped inside your home.
- Installing a whole-house or portable de-humidifier can greatly reduce the amount of moisture in the air. Automatic models contain sensors that activate when a certain level of humidity is detected.
- An air to air exchanger works through your HVAC unit to bring in fresh air from outside while sending interior air outdoors. These units remove pollutants from your home as well as moisture.
- Gas fireplaces release high levels of moisture when they burn, which can contribute to high humidity levels. Running a de-humidifier when the fireplace is on will help reduce those levels.
Invest in an inexpensive hygrometer to monitor the effects of the changes you made in different areas of your home. If your windows or interior humidity levels don’t seem to be the problems, ground moisture may be moving up through the foundation of your home. An inspection by your local building inspector may be able to pinpoint the cause of the condensation issue.