Window condensation is one of the most common homeowner frustrations – especially during seasonal temperature changes.

While it may look like a problem with the window, condensation often indicates an issue with indoor humidity or insulation.

Learn when condensation is normal and when it’s a sign you need window replacement services.

Window condensation is usually caused by warm air inside the home touching a cold window. When the warmth of the air meets the cold surface of a window, it turns into water.

Condensation often appears as:

• Minor: With some water droplets lining the edges of the window.
• Moderate: A wet, “fogged up” appearance across the whole window.
• Severe: The whole window is dripping wet, with running water droplets and pools of water on the window ledge.

When warm air meets a cooler surface (like glass), water droplets can form. This only happens when the air and the surface meets – what’s known as – the dew point.

In simple terms, the dew point is the temperature the air must be cooled at for it to turn to liquid on your glass windows.

There are several known “levels” of dew points, which are as follows:

• Under 55°F: This dew point means the air is dry and comfortable.
• 55°F-56°F: This dew point can make it feel nice and comfortable or a little “sticky”.
• Above 65°F: This dew point can make the room feel humid, sticky, and uncomfortable.

The main types of window condensation include interior, exterior, and between-the-panes condensation:

• Interior condensation: Signs include foggy windows, water dripping on the glass, water droplets around the edges of the window, and mold growth around the frames/on the walls.
• Exterior condensation: Signs include seeing moisture on the outside of the window (not inside the home), which usually disappears when the sun comes out and dries the glass.
• Between-the-glass condensation: Signs include seeing moisture trapped inside the glass, where you can’t touch or wipe it away from inside or outside the home.

The cause depends on the type of window condensation.

Seeing water droplets, fogginess, or moisture on your windows indoors is a sign of interior condensation.

This can be caused by:

• High humidity (over 50%, but usually in the high ranges between 70%-90%)
• Poor ventilation
• Houseplants
• Cooking
• Showering
• Opening windows/doors frequently when the air outside is drastically hotter or colder than the air indoors

This type of condensation is a cause for concern, as high humidity in the home can lead to mold developing around your windows. However this is not an issue with your windows and instead means you need to adjust the humidity in your home.
Over time, this can cause health issues and damage to your window frames and seals.

Exterior condensation isn’t usually anything to worry about. In fact, it’s often a sign that your windows are very energy-efficient and you have good insulation in your home.

This type of condensation is usually caused by cool or humid air outside the home hitting your windows. Generally, it disappears on its own, when the sun warms up the outside of your windows.

Condensation trapped between your windows is a problem, and it doesn’t usually have an “easy” or quick fix. It can happen on double or single-pane glass windows.

What causes this type of window condensation is usually:

• Failed seals: The most common cause is that the seal between the window has worn away, allowing water to seep inside the glass. You can replace your seals, which can get rid of condensation.
• Saturated desiccant: This happens when you’ve had a broken seal for too long. The desiccant is a drying agent inside the glass that absorbs moisture. When it becomes too wet, it won’t work anymore.
  Blocked drainage channels: Weep holes allow any moisture that gets on or into your window escape. Condensation occurs if these become clogged with dirt, paint, water, or debris.
• Poor installation: Unfortunately, condensation can be caused by poor installation. If the window was not installed with a tight seal, or if it wasn’t completely level, it can fail.
• Old windows: Window seals, drying agents, and extreme weather can – over time – cause windows to degrade. This can especially happen with older, less modern windows.

The only fix for this is to replace your glass, or you may want to replace the entire window if there are other issues with it. Glass replacement is a less expensive solution that we offer, however it may not fix all of your issues if the window is also rotten, drafty, or has other damage.

Learn more about window replacement services at Schaaf Windows.

You can often reduce or get rid of window condensation entirely by changing your daily habits and installing items to manage humidity.

Common, effective ways to remove window condensation include:

Stagnant air and poor circulation can cause high humidity and window condensation. Ways to improve indoor air circulation include:

• Opening vents: This lets trapped air escape and fresh air in.
• Running ceiling fans clockwise in winter: This helps air circulate when windows are unlikely to be opened (e.g., when it’s cold).
• Using extractor fans: These are often fitted in bathrooms or kitchens and usually run when the lights are turned on.
• Opening doors/windows: This can improve air circulation, but be mindful that if it’s cold outside and warm inside, or warm outside and cold inside, it can lead to even higher humidity levels. Only do this when temperatures are similar inside and outside.

The best way to manage humidity levels in a home is to run a dehumidifier in moisture-prone areas. This is a plug-in machine that gradually takes moisture out of the air in your home.

It works best when placed in high-humidity areas, like kitchens, bathrooms, basements, or areas with interior window condensation.

Ideal indoor humidity levels are between 30-50%. You can check exact humidity levels in your home using a hygrometer or dehumidifier.

Signs of high humidity include seeing water on your windows inside the home or mold developing near the windows.

In some cases, the best fix for window condensation is to replace your windows with energy-efficient styles, which have better seals.

The best type of windows for improving energy-efficiency and insulation are low-emissivity windows. The Low-E coatings and argon gas help regulate temperatures and minimize condensation.

Read about energy-efficient windows and the benefits for your home.

In some cases, window condensation can be a sign that it’s time to replace your windows. Common signs a window needs replacing include:

• Persistent fog/water droplets between the panes
• Visible mold on the window seals or frames
• Excess water on the seals
• Drainage holes you can’t unclog
• Drafts coming through the windows when you put your hand near them
• Difficulty opening or closing your windows

At Schaaf Window, we provide a professional, free assessment of your windows. With 65+ years of experience, we can inspect your windows and advise on the best replacement options for your home.

Learn more about our window replacement services.

Good maintenance can prevent window condensation and protect your seals from degradation.

Effective ways to care for your windows include:

• Wiping down frames
• Keeping weatherstripping clean
• Regularly inspecting drainage holes
• Lubricating hinges/locks routinely
• Cleaning debris from tracks

Read more maintenance tips to take care of your windows.

At Schaaf Window, we are a trusted window supplier and installer in Illinois and Indiana.

Our team of professionals are certified installers with long-standing expertise. We take pride in delivering exceptional service to ensure your new windows suit interior styles and withstand the test of time.

Schedule an inspection for a professional assessment of whether your condensation issue is normal – or if it’s a sign it’s time for replacement.