Why windows condensation is caused and how to prevent it

We’ve all experienced our windows appearing foggy or covered in condensation.  Condensation is formed by humidity or water in the air that lands on the glass in windows.  During the summer months, the same thing happens if you are outside with a very cold drink, the glass will form condensation.  Why?  Glass is cooler than other materials and is one of the coolest places in your home causing the natural formation of condensation.

That said, condensation does not only happen when the air is warm, condensation will also form during the winter. I’m sure you’ve noticed during the winter months your windows fogging up or forming condensation.  This is caused by the humidity inside your home.

You might not realize there are several other factors that will cause condensation.  For instance, if you are cooking something on your stove, your windows will fog up from the humidity building up in the kitchen.

What Other Factors Will Form Humidity Inside Your Home?

On a scientific level, when the temperature of the glass in your windows drops below the dew point of the air, condensation will form.  Dew point is when the temperature’s water vapor condenses into water.  The higher the level, the higher the moisture in the air.  At some point, the air cannot hold the moisture any longer so it releases it as a liquid on to your windows.

There are several reasons why humidity in a controlled climate will add to even more condensation including:


When you are using water to cook, taking a shower, or washing your dishes, this added moisture will be released into the air. There are other natural factors that you don’t even think about.  When you breathe or sweat, you are producing a buildup of moisture inside your home.  There really is nothing you can do to prevent it, so I wouldn’t suggest you stop breathing!

House Plants

If you have house plants, you will have a higher level of humidity in your home.  As a plant takes in water through its roots, the water will be released through its leaves then evaporates into the air. This process is known as transpiration.

The more plants you have the more humidity will build up in your home. There are a few plants that are considered the leading culprits such as English Ivy, Areca Palms, Peace Lilies, and Spider Plants.

Structural Problems

Other factors could include structural issues such as leaks that have developed over time.  Moisture will find its way indoors through cracks that have formed in your roof, an overlooked leaky pipe, or even the separation of a windowsill joint.

The Lack Of Good Ventilation

The lack of good ventilation will not only cause condensation but can be unhealthy.  There are certain rooms in your home that have very poor ventilation such as your bathroom.  This is why most bathrooms have built-in fans for ventilation to prevent the buildup of humidity and other conditions such as mold which is very unhealthy.

Decrease Window Condensation By Reducing The Humidity

If the humidity in your home is out of control, you might want to take some of the following suggestions into consideration:

If you have a humidifier in your home and it’s running around the clock, it’s time to turn it off for a while.  Humidifiers are just that, they add moisture to the air.  Most humidifiers are commonly used during the winter months as the air is so much dryer.  They are fantastic for relieving dry throats, dry skin, dry eyes, and can provide relief from allergies and asthma.  Unfortunately, most humidifiers release far too much moisture, causing very high levels of humidity.

You should consider lowering the level of hot water when taking a shower. Bathrooms, in general, have poor ventilation and the hotter the water, the higher the humidity. We are not suggesting you take a cold shower, just lower the temperature a bit.

While on the topic of bathrooms, make sure you have proper forms of ventilation installed.  If your bathroom does not have one, exhaust fans are excellent alternatives that can be easily installed by a professional.

You should also have good ventilation in other rooms of your home, especially during seasons when the humidity is very high. Fans should be run for a few minutes during the day, whether stand-alone fans or ceiling fans.

Appliances that produce humidity can also cause a reverse draft through your chimney.  During the summer months, the hot air from your roof will travel down your chimney making the air in your home very sticky and uncomfortable. You should make sure your fireplace damper is open.

Make sure all your appliances have proper ventilation such as your stove and your clothes dryer. Proper ventilation should drag excessive moisture outside bringing the level of humidity inside way down.

If you have louvers in your attic and/or basement, check them from time to time to ensure there are no cracks or spaces from aging.  Louvers are great for windows in order to bring in the air while keeping moisture out.  Therefore, make sure the louvers are left open for good ventilation, especially in these two areas of your home where humidity and heat will climb very quickly.

You might want to consider adding a dehumidifier to your basement if you do not have louvers.  Basements are known for producing moisture and dehumidifiers will take that moisture out of the air.  This is an excellent option if you live in a climate known for high temperatures and high humidity, such as Florida.

If you have the option, dry your clothes outside on a line instead of running your dryer.  One, your clothes will be exposed to fresh air.  Two, your home will be free of hot air.

If you have central air condition, make sure to change out the filter on a regular basis.  Central air conditioning units work just like a dehumidifier and if run regularly, will keep the humidity in your home way down.

A good way to keep condensation off your windows, make sure your air or heat is set at a constant temperature.  It will greatly decrease humidity and keep condensation away.

If you are lucky to have ceiling fans, make sure you run them regularly to circulate the air in the room.  Make sure you set the fans to run counterclockwise during the summer months and clockwise during the winter months.

The above are a few good suggestions to lower humidity, heat, and condensation from your windows and home.  Now it’s time to learn what the right level of humidity should actually be in your home, so please read on!

Finding The Correct Humidity Level For Your Home

Believe it or not, your home should have a certain level of humidity for greater comfort and overall better health.  The following chart will give you a good idea what the maximum humidity level should be in a home heated up to 70° F.  Keep in mind, the higher the temperature is inside, the lower the humidity level should be.

If you would like to have a more accurate reading of what your humidity level should be, you might want to purchase a hygrometer.  This is a really inexpensive tool to monitor your levels of humidity and will easily help you make changes in your home when needed.

You will be able to determine what activities are causing a rise in your humidity level such as taking a shower.  You will also be able to easily adjust your temperature with the change of seasons. Also, using a hygrometer will help you find out if you might have an area where moisture is entering your home, possibly damage on your roof or a dysfunctioning window seal.

There are a few things you might have to consider regarding your windows and condensation.

Window Condensation – What To Look For

If you live in an area where humidity and high heat are common during the summer, you will have a certain level of condensation on your windows.  You might try opening the window for a short time to balance out the temperature inside and lower the moisture levels.  That said, there are situations when window condensation can be a problem:

If you have double or triple pane windows, you know how wonderful they are for saving energy.  Unfortunately, you might discover condensation has been trapped inside the panels.  If this happens, you might want to have the window checked out for a possible seal failure. If the window looks dirty inside, moisture has gotten in between the panes and all you can do is call a window expert to come out and fix the problem.

If you notice excessive moisture around your window and in the window frame, window sills, and your walls, you need to address this as quickly as possible. This problem can easily cause mold and mildew on your walls and windows as well as cause the paint to peel from your windows, leading to serious damage.

If you are continually battling with window condensation, it might be time to consider getting replacement windows.  We will now cover why new windows can possibly prevent condensation.

New Windows Might Be The Solution For Condensation Issues

First off, you should consider how old your current windows are.  If they are over 15 years old, it’s probably a good idea to get them replaced.  Some people think all they have to do is replace the glass in their windows but that will not necessarily cure the problem of condensation.  You must inspect your windows very carefully for signs of mildew, rot, and mold.  If any of these signs are present, you should seriously consider replacing them.  On top of that, if you presently have single-pane windows, you are not saving energy, you are spending more.

There are several advantages for replacing your windows. Replacing your windows will eliminate condensation between the panes of glass because there will be new seals that your old windows no longer offer. You will not constantly experience the build-up of condensation, instead, your windows will be nice clean, clear looking.

Studies have shown that double pane windows use argon gas and low-E glass to reduce the build-up of condensation,  The features of double pane windows allow for 37% humidity without indoor condensation. This means if it’s 70°F indoors and zero degrees outside, there will be no condensation on your windows.

I Have New Windows – So Why Is There Condensation?

This is actually very common and there is no need for you to panic, just take a deep breath.  Condensation can possibly form on new windows because they are actually working properly!  Your new windows have excellent insulation, not having any air leaks.  This condensation will only last for a very brief period of time and within the next couple of weeks, the condensation should be completely gone!

Is There A Way To Know Where The Condensation Is Coming From?

Unfortunately, it can be a little difficult to know exactly what is causing condensation on your windows.  If you are experiencing a lot of “sweat” on your windows, we can help you out! We will come out and inspect your windows and let you know if you are truly experiencing unhealthy, serious condensation or not.

Please feel free to contact us with any questions or concerns you might have.  We are here to help you learn how to get rid of bad window condensation once and for all!

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