Condensation on a window featuring all-season Climate Seal window inserts.

Condensation is something that puzzles many of us when we are young. We wonder how our cold drink makes its way onto the sides of the glass on a hot summer day and why the grass is wet in the morning when it didn’t rain the night before. It’s an interesting curiosity, but it seems harmless enough.

As we grow older, we realize that condensation in unusual places can be a sign of trouble. We want to know why it’s there. Condensation on windows can have us wondering whether they need to be repaired or replaced. The answer depends mainly on where the condensation forms and the weather conditions outside the home. Some condensation is harmless and may even point to the fact that your windows are working the way they should, while other condensation should have you rethinking your timeframe for getting new windows.

What is condensation?

First and foremost, let’s look at what condensation is and how it forms. Basically, when the surface temperature of an object is lower than the dew point, we see condensation.

We see condensation on the sides of a cold glass on a warm day because when the humidity in warm air comes into contact with the cold surface of the glass, it turns from a gas to a liquid. That excess moisture collects as water droplets on the sides of the glass.

This same simple concept can be applied to any place we see condensation. When the grass temp is cooler than the dew point, we see condensation. When we blast warm air onto a cold windshield, again, condensation. Condensation on your windows is formed the same way, but the location can lead to different diagnoses when trying to eliminate it.

What causes condensation on windows?

There are a number of reasons we see condensation, and they range from things as simple as the bathroom window steaming up while you shower to window failure that can lead to higher energy bills and mold. A good indicator of what’s going on in your home is the location you see the condensation collecting.

Condensation on the outside of windows 

When we see condensation on the outside of our windows, it often occurs because the temperature of your window pane has fallen below the dew point. This usually isn’t a bad thing. It means your home is energy efficient, and your windows are well sealed. If you’ve got air passing through gaps in the window frame, the surface temperature of your window pane may not be able to drop low enough to create condensation. While there’s a slight chance, this type of condensation will do any real damage, learning how to stop condensation on windows can slow its accumulation.

Wait it out

While this may not be what you want to hear, exterior condensation will usually go away on its own if you are patient enough to wait for it. Condensation on your windows will disappear through the day as the sunlight raises the temp of the glass. It’s possible you’ll be left with some water spots, but the moisture will most likely be gone by late morning.

Squeegee it off

If you’d prefer to have it gone immediately, and you’ve got a squeegee that can safely reach the windows, you can always go that route. I’m not the type to wipe away something that will take care of itself in a few hours, but to each their own. While you’re out there, hit them with some window cleaner to prevent water spots on days you feel too lazy to wipe them down.

Apply Rain-X

If you ever get tired of wiping your windows dry, try applying Rain X. It coats the glass and fills in any porous parts of the panes, and causes the droplets to run off on their own. Any moisture that’s left will exist in such small droplets that you probably won’t even notice them. Less moisture means the condensation evaporates more quickly, and you don’t have to deal with any water spots.

Condensation on the inside of windows

We see more interior condensation on windows in winter because we generally keep all our windows shut tight, and our fans are turned off ‘til spring. This means we don’t experience the same amount of circulation in the home that we do in the warmer months. We can open up the windows or run our fans in reverse to help with the circulation, but there are some other steps you can take to keep your windows clear and dry without opening your windows to the frigid winter air.

Lower the humidity in your home

Since the most common cause of interior condensation on windows is having too much humidity in your home, keeping your humidity levels in check is the first step in eliminating your condensation issues. Pick up a hygrometer, which measures indoor humidity levels, and see what you’re dealing with. Set a target humidity level, and take steps to get there.

What is the ideal humidity in a home? According to the Mayo Clinic, the ideal humidity range for your home is between 30 and 50%. This range is optimal for both health and comfort. If you have possessions sensitive to humidity, like wooden instruments or expensive cigars, they may drive the humidity level you ultimately choose. Humidifiers and dehumidifiers are great tools to help you dial in the perfect level.

Close the bathroom door

While ventilation is a good thing when we talk about removing humidity from your home, the tables turn a bit when we are bathing. Taking hot baths and showers releases an incredible amount of steam into the room. Closing the door will prevent it from traveling to other areas and steaming up windows throughout the house.

Always use the bathroom fan

Now that you’ve confined all that steam to a single room, it needs somewhere to go. The fan is a powerful bathroom dehumidifier. Turning on the fan when you bathe allows the steam produced to immediately exit the home. It may even speed up your morning routine by helping to clear the mirror more quickly.

Be mindful when cooking

Another thing that we regularly do in our homes that creates a lot of steam is cooking. When you’re boiling a pot of water or simmering something on the stove, placing a lid on the pot will reduce the amount of moisture that gets released into the air. If you’ve got a decent extractor fan, that will help push the steam outdoors the same way your bathroom fan does.

Make sure your fans are in working order

With all this talk about fans, it’s important to make sure they are all working properly. The fans in your bathroom, kitchen, and on the back of your dryer all remove excess moisture from areas that produce a lot of it. They can’t do their jobs if they don’t work well. If your fans aren’t moving as much air as they should, consider servicing them or cleaning the ducts to improve airflow.

Condensation between window panes

This is the type of condensation you definitely don’t want to see when it comes to your windows. Water vapor between the panes usually means you have a broken window pane or seal, and the gas that’s put there to keep the window energy efficient has leaked out. 

You can try cleaning the window really well to make sure you aren’t mistaking some discoloration for water vapor. Sometimes the cleaning products we use can leave a residue that resembles condensation inside the window unit. If what you’re seeing is, in fact, condensation between the panes, you should consider replacing the window. It’s no longer energy efficient and will only get worse down the line.

Eliminate condensation from your life

Now that you understand a little more about what causes condensation and how to prevent condensation on windows, you can use that knowledge to discern whether or not your condensation is cause for concern. Whether you need a whole new set of windows or can solve your problems with a quality set of window inserts, eliminating excess moisture will do you and your family a world of favors when it comes to maintaining your health and your home. It’s a great feeling to kiss condensation on windows goodbye.


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