Window Condensation Guide: How to Prevent Window Condensation

Window Condensation Guide - How to Prevent Window Condensation

Foggy windows can be annoying and unattractive. Window condensation, also called “sweating,” is often the first sign of excess humidity in your home, which can lead to mold and other damage. It can also be a sign of damage to your windows and a lack of energy-efficiency in your home. Any of these reasons can be a cause for concern for homeowners.

So, how can you prevent window condensation and mold? Depending on the root cause of the moisture buildup, you may need to replace your windows or find ways to limit the humidity in your house. This window condensation guide can help you get to the bottom of your problem and find the solutions you need.

What Causes Window Condensation?

What Causes Window Condensation

Condensation happens when the air becomes humid. All air contains some moisture, and many of the activities we do add to the humidity in the air. Anything from showering to mopping the floor adds water to our indoor environments. When warm, humid air touches a cold surface, the air contracts, and condenses as it cools. The condensation results in water droplets forming on the cold surface. You’ll commonly see condensation on the outside of a glass of ice water or a car first thing in the morning.

There are many reasons why you might find condensation on your windows. Window condensation is most common in the winter, when the temperature gets below 35 degrees outside and there is a higher temperature disparity between indoors and outdoors. The cold air touching the outer pane cools down the window, putting it in contact with the warm, humid air on the inside. The outdoor air is also drier in the winter, which further contributes to the issue.

What Causes Window Condensation on Your Home’s Exterior?

Condensation is a good thing when it occurs on the outer surface of the window. Outside condensation occurs when the air outside is slightly warmer than the indoor temperature of the window. When the temperature is mild, and you have well-insulated windows, your windows stop the transfer of heat from outdoors to indoors, causing condensation. It’s a sign that your window is doing its job and insulating heat. As dew forms on the grass, it also forms on the exterior of your window.

What Causes Window Condensation on Your Home’s Interior?

When condensation happens on the inside surface of the windows — that is, when you can touch it, and your finger gets wet — it’s a sign of more humidity in the air. It’s not usually a problem with the window itself. Instead, it means the air in your home has an above-average moisture level. You might also have poor ventilation. An unusually wet and humid home environment may cause mold buildup and structural damage to wooden surfaces.

If it’s happening only on one particular window, it might be a sign of a draft. As moist air enters your home through an air leak in one of your windows, condensation will build up on this window first. If you see moisture buildup around one window, feel around for air leaks. If you spot any, it’s best to have the window resealed to keep your home energy efficient and free of excess moisture.

What Causes Window Condensation Between the Glass Panels?

The biggest issue for windows is when condensation occurs in between the two panes. You can’t wipe off this is condensation from the inside or outside your house. In a double- or triple-paned window, there are two or three pieces of glass held by one window frame. The gap between the panels is usually filled with an insulating gas such as argon. These layers of glass have an airtight seal. Condensation builds up on the inside of windows when this seal breaks.

You might be able to get rid of this fog by cleaning the outer surface of the window to eliminate some moisture. Otherwise, you may need to replace the panes or the entire window.

Why Older Windows Build up Condensation

Why Older Windows Build Up Condensation

When old windows build up condensation, it’s most often a sign that you need to replace the window or its panes. Older windows may simply let more moist air into your home, causing more condensation. They may also start to wear out. If you have had your window for more than 15 years, it might be time to upgrade to new windows. New energy-efficient windows will be more airtight, causing less condensation. There are a few things to look for with old windows that may be the cause of your condensation.

1. Broken Seal

If an old window is showing signs of moisture buildup between the panes, it may have a broken seal. Most insulated windows have a double seal that can withstand opening and closing. The inner layer of the seal protects against moisture and other damage, while the outer layer of the seal provides added strength to the window. Most windows also have a spacer, known as a desiccant. The desiccant is a tube that contains moisture-absorbing chemicals.

Window seals are very durable and have a lifespan of 10 to 20 years. When one of the seals breaks, the other can usually manage on its own for a while. At the end of its lifespan, the seal may naturally start to wear out. The seal can also break because of water buildup in the window frame and improper window drainage. The more direct sunlight a window gets, the more the panes expand and contract, which also weakens the seals over time.

2. Air Leaks

Older windows are also more likely to spring air leaks. If only some windows are experiencing condensation, these windows are likely letting in moist air from the outside. If you suspect air leaks, inspect your windows for signs of leakage. If you see any cracks or gaps in the window frames or the exterior caulking, outside air is getting through. You might also feel cold air when you hold your hand near the edges of the window.

If you do find air leaks, you may be able to eliminate condensation by recaulking the windows. In this case, you should remove the old caulk and reapply. When caulking your windows, make sure the temperature is above 45 degrees and that there is relatively low humidity, so that the caulk can set properly. Significant leaks in the window frames may warrant replacement. A window professional or contractor can help you detect and repair air leaks and let you know when replacing is necessary.

3. Single-Pane Windows

Homes built before the 1980s may feature single-pane windows. Most modern homes have double- or triple-pane windows, which have much better insulation. Single pane windows are less energy-efficient and are more likely to let in moist air. They don’t have an airtight seal or an insulating gas to lock out air. Just as air leaks let in wet air from outside, single-pane windows can let in water vapor after rain or humid weather.

If you have old single-pane windows, it’s a good idea to replace them with double- or triple-pane windows. You’ll enjoy exceptional energy-efficiency, which will help you save on heating and cooling costs. You may also experience less moisture entering your home via your windows, which means less interior condensation.

Why Newer Windows Can Build up Condensation

When appropriately installed, new windows may still experience some condensation. It’s not usually a problem with the windows and is instead the first sign that your house has higher than average humidity levels. There may be a few reasons why there is condensation on your new windows. If you suspect your windows were installed incorrectly, contact a licensed professional contractor to help you decide on the best course of action. 

1. Better Insulation

Energy-efficient insulating windows keep warm air inside and cold air outside. If you’ve just installed new windows, they are likely much more insulated than your old windows were. While your old windows let air flow more freely between the outdoors and your home, your new windows create an airtight barrier. That insulation can also keep more moist air inside your home, with fewer ways for the air to escape. In this case, finding ways to reduce the humidity without compromising the energy-efficiency of your home is critical.

2. New Construction or Remodeling

If you’ve ever tried to light a fire with freshly chopped wood, you know that new wood is moist and takes a long time to dry out. If you’ve just installed new windows, they may have a new wooden frame. You also may have taken on some new construction or remodeling. A newly-built or recently-remodeled home will have wood that’s still a bit wet. It usually takes about a year for this wood to dry out, and you’ll have a little excess moisture in the meantime.

The good news is that this humidity will naturally clear out of your house with time. You can take some measures to dehumidify your home if the window condensation bothers you. Turning on some fans to circulate the air and occasionally opening windows and doors to let your home air out may be useful.

3. Humid Summers or Extreme Temperatures

In the summer and autumn, your home is more likely to pick up extra moisture from the damp air. You might be opening windows and doors more often because the weather is nice. Open windows could let in more humidity. Your house absorbs water vapor during the wet summer months. Then, when you turn the heat on come autumn, the moisture inside your walls, floors and ceilings warms up and evaporates back into the air. The humidity should go away after a few weeks of heating your home.

Extreme temperature shifts can also cause more condensation. Because condensation occurs when warm air touches a cold surface, when the weather shifts rapidly, there’s more likely to be a disparity between indoor and outdoor temperatures. An occasional weather-related temperature change may cause some sweat, usually around the times the seasons change. This condensation is nothing to worry about, as it will go away as temperatures stabilize.

How to Prevent Window Condensation

How to Prevent Window Condensation

If there is nothing wrong with your windows, the key to fixing window condensation is to curb the moisture in your home. Here are seven steps you can take to bring down your house’s humidity levels.

1. Check Ventilation and Use Exhaust Fans

If your home experiences condensation year-round, it may be a sign of poor ventilation. A first step to overcoming this problem is to check all sources of ventilation to the outside. Your kitchen, bathroom and laundry room should all have an exhaust fan. It’s essential to use the exhaust fan whenever you produce steam in your home. Whenever you shower, boil water or do laundry, turn on the nearby exhaust fan. Make sure it stays on for an extra 15 to 20 minutes afterward.

2. Air out Your Home

Occasionally airing out your home can help you get rid of excess humidity. To air out your home, open windows for a few minutes each day. Opening the windows will let stale, moist air escape so cool, dry air enter. Just a few minutes a day won’t impact your heating. You can get even more moisture-removing power out of this method by using fans to circulate air around your home. Ceiling fans rotating clockwise will push rising warm air back towards the floor.

3. Open Your Attic and Basement Louvers

Another way to let air escape your home is to open the louvers in your attic and basement. These slatted vents help ventilate your home in the two areas that need it the most. These are areas where you do not usually spend a lot of time, so you might not pay attention to their climates. Louvers or gable vents can create some extra ventilation in your basement and attic, so open them and make sure they are working correctly.

Another thing to try is opening your fireplace damper. You usually want to keep this closed to prevent heated air from escaping when you don’t have a fire going. When moisture in your home becomes a little excessive, opening your chimney flue can release some extra humidity.

4. Turn Down Your Humidifier

All air has some level of moisture in it. The recommended amount of moisture changes depending on the outdoor temperature. With the correct settings, your home’s humidifier will help you adjust your indoor moisture levels. If you’re concerned about the level of moisture in your home, check your humidifier settings. Follow the Environmental Protection Agency’s guidelines to control moisture buildup in your home.

Outdoor Temperature Indoor Relative Humidity
+20o F 35%
+10o F 30%
0o F 25%
-10o F 20%
-20o F 15%

5. Try a Dehumidifier

If adjusting the settings on your humidifier isn’t enough, you can try a dehumidifier to suck more vapor out of the air. A full-sized dehumidifier will cost a few hundred dollars, and a mini one will be more affordable. Both can help you take moisture out of your home. Some work automatically when the air gets too damp, while others you will have to turn on yourself.

6. Consolidate Your Houseplants

A few plants can brighten up your home. They can also make your home look and feel like the rainforest. Houseplants can release moisture into the air just as new wood does. You can curb the extra humidity by keeping all your houseplants in one area of your home. Also, take care not to over-water them. Keeping them away from windows can help you reduce condensation.

Fireplace logs are another common culprit for water vapor, especially if you keep them outside or in your basement before stacking them by the hearth. If you can keep your firewood elsewhere until you’re ready to build a fire, you may eliminate another source of moisture.

7. Turn up the Heat

Many temporary and weather-related sources of moisture go away after a few weeks with the heat on. Both occasional and regular water vapor can dry out with heat. Making your windows themselves warmer can also eliminate condensation. Remember that condensation forms on cold surfaces. By turning up the thermostat, the glass on the windows becomes warmer and less likely to sweat.

Replace Your Windows With Sunshine Contracting

Replace Your Windows With Sunshine Contracting

If broken or damaged windows are letting excess moisture into your home, you might not be able to solve the issue by taking humidity out of the air. Window condensation on the inside window surface can sometimes be caused by damage to the window frame or air leaks. Condensation between the panes is almost always a sign of a problem. If you suspect your windows need replacement, contact Sunshine Contracting today for a free in-home consultation.

Sunshine Contracting is a Virginia-based, family-owned local business with nationwide renown. We have been named one of Qualified Remodelers Magazine’s Top 200 Exterior Remodelers in the Nation for more than 10 years in a row. We offer fast, professional service and quality that will last for years to come. If you’re ready to give your home beautiful, well-insulated new windows, Sunshine Contracting is the team for you.


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