How to Prevent Window Condensation

Jan 22, 2021

What Window Condensation Really Means

Not all window condensation is a problem – sometimes it’s a good thing. Here’s how to tell what’s causing condensation or fogging on your windows and what to do about it.

How to tell when you have a window condensation problem.

Are you noticing moisture on your window panes? Here’s how to tell when window condensation is totally normal, when it indicates a real problem with your windows, and how to reduce the likelihood of moisture accumulating where it shouldn’t.

Window Condensation

What causes window condensation?

Condensation occurs when moisture in the air settles on a cooler surface. We see normal condensation in numerous ways every day, like:

  • Steam from your shower condensing on your bathroom mirror
  • Humid air condensing on your glass because of iced tea on a hot day
  • Eyeglasses fogging up when you walk into a warm house on a cold day

Condensation isn’t caused by the glass in any of these situations; the glass is simply the landing place for moisture that exists in the surrounding air. Your home’s windows are another cool surface that allows for condensation. And with two panes of glass in most windows, you may see condensation on the room-side of the window, on the window glass on the exterior of your home, or possibly between the panes, depending on the conditions.

Does Condensation Mean My Windows Are Broken?

More often than not, condensation or fogging on your windows does not indicate a problem with your windows. In some cases, it may actually indicate that your energy-efficient windows are doing their job. Identifying the cause of window condensation can also help you manage your home more efficiently overall.

Here are three scenarios to watch out for:

Excess Indoor Moisture

The next time you notice window condensation or fogging inside your home, swipe your finger across the foggy area. If the glass feels wet and your finger leaves a trail, you have moisture collecting on room-side of your window glass. This is an indication that your home’s indoor humidity is too high.

What does that mean? In some cases, excess indoor humidity is normal. But a constant high-humidity environment can lead to mold growth on wood framing and drywall, and poor indoor air quality, both of which can lead to health problems. 

Here are a few causes of excess indoor humidity and what you can do about it:

Frosty Window

Solution:

This condensation is normal and temporary; it will evaporate on its own as the space returns to a normal humidity level. Running an exhaust fan in the bathroom or the range hood in your kitchen can keep this condensation at bay.

Solution:

During dry winter months, it’s common to run a humidifier in your home. Some HVAC systems even have offer whole-house humidification. The ideal indoor relative humidity level is 30-50% depending on the outdoor air temperature. Refer to your humidifier’s manual for the best way to set and run the unit to achieve this.

Solution:

Outdoor air finds its way into your home through all kinds of gaps and cracks, especially around older, uninsulated windows and doors. When outdoor humidity levels are high, that excess moisture enters your home with the rest of the outdoor air. If you notice indoor condensation on windows that aren’t otherwise affected by steam or humidity from other sources, it may be time to air-seal your home or replace your windows. (Take our one-question quiz to see how much longer your current windows will last.)

Excess Outdoor Moisture

If the same swipe test reveals condensation on the exterior side of your windows, it’s a good indication that your windows are working the way they should. The best dual-paned, energy-efficient windows are designed to reduce heat transfer through the glass from both inside and outside the home. What does that mean?

Just like in your steamy bathroom, moisture in outside air will condense on cooler surfaces. We often see this as dew on the grass, but your windows also offer a perfect surface for condensation. If the surface temperature of your window glass is lower than the dew point, you’re likely to see condensation on the outside of the window. This indicates that your energy-efficient windows are keeping the warm air inside your house, and not transferring it to the exterior pane of glass – exactly how they should work! As the sun warms the exterior glass surface, the dew will evaporate.

Dayton windows
Replacement Windows Columbus

Moisture Between Window Panes

If you try the swipe test and can’t feel or remove the condensation from the surface of your window glass, the problem could be moisture trapped between the window panes. Unfortunately, this problem has no easy solution.

As we mentioned, most energy-efficient windows have two panes of glass. The space between the panes is filled with an insulating gas such as argon. Over time, the seals keeping the argon in place can deteriorate. Most windows seals break within 5 to 7 years.

Here’s what happens next:

#1 – As the argon gas escapes, the window loses its energy efficiency and will no longer be able to prevent heat transfer through the glass.

#2 – Air surrounding the window enters the gap between the panes and fills the space the argon gas has left.

#3 – Any moisture in the incoming air will now condense on the interior face of the glass, causing fogging between the panes. This moisture is inaccessible and cannot be removed.

#4 – Once seals break, the problem will only get worse and lead to more issues

    • Excessive fogging or condensation will make it impossible to see through the window glass.
    • Moisture can cause rusting of internal metal components, such as metal window spacers
    • When the window gets hot, trapped moisture can expand, threatening the structural integrity of the glass, sash and window frame.

Once moisture starts condensing between the window panes, there’s no way to remove it. If the fogging is minimal or unobtrusive, you can try sealing the edge of the glass with clear silicone to possibly prevent more moisture from getting in. However, doing this could void the warranty on your windows, and does nothing to recover the lost energy efficiency.

The only option to eliminate condensation trapped between your window panes is to replace the affected sash. A new sash with an intact seal will help the window perform at its best and maintain the structural integrity of the entire window unit.

Window Installation

How to Replace a Window with a Broken Seal

If your windows are already experiencing condensation between the glass, reach out to your window installer or manufacturer to discuss replacing the sash. Unfortunately. broken window seals are usually not covered by window warranties, so the replacement can cost several hundred dollars for a sash by itself, or much more for an entire window replacement, including the cost of labor.

Improveit window customers don’t have to worry about this extra expense! All Improveit Performax54 windows come with a complete, transferrable lifetime warranty that covers everything – including broken seals. Our No Seal Failure Guarantee means that if any window installed by Improveit experiences a broken window seal, we’ll solve the problem at no cost to you.

Give us a call at 855-637-2999 to learn more about our unbeatable window warranty and how to protect your windows against seal failure forever!

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