What Causes Window Condensation

Being a builder and home improvement contractor, I’m always asked what seems like a million home improvement questions from friends and family of mine. However, the type of question I’m often asked the most around winter time and summer, is what causes window condensation. So I thought I’d put my best foot fourth and try to help out someone whom might be concerned about window condensation in their homes.

Window condensation in most cases boils down to how your home was built, plain and simple. New residential homes nowadays are being built with better building practices and materials to ensure high energy efficiency ratings. For example, improved insulation, tighter vapor barriers and a higher quality energy efficent air filtration system to name a few. With all of these energy efficient improvements, results in having “air tight” home. Having an “air tight” home isn’t necessarily a bad thing, don’t get me wrong. Having a “air tight” home is what keeps are heating and cooling bills low, more energy efficient.

For many, the biggest culprit in window condensation is the level of humidity in the air. Humidity is basically (water vapor in the air) humidity is a way we measure how much mositure is in the air. Water vapor is created in many ways around the house. For example, taking your everyday shower, washing and drying your clothes, cooking, your plants around the house create moisture, breathing creates moisture. Take a look at your window after you’ve had a shower, it will be dripping in moisture – unless you’ve your bathroom exhuast fan running..

So what is condensation? Condensation is formed when water vapor comes in contact with a cool surface such as your windows and then transforms back into a liquid state on your windows. So for condensation to form on your windows, the temperature of your windows must be below or at the dew point of the air touching the glass. Have you ever had a cold drink on a hot day? Have you noticed what happens to the outside of your glass? It begins to build moisture on the outside of the glass cup.

Condensation in Older Homes V’S Newer Homes

In my experience as a home builder, homes built before 1960 don’t really have this problem. The reason for this, is because most homes built before this era didn’t get all of the extra treatment newer homes get in regards to insulation, vapor barriers, air filtration systems, etc.. So in essence, are more prone to drafts and air leakage. This helps with keeping moisture out of the home and the walls breathing. The only down side to this, is higher energy bills.

How To Stop Window Condensation

Well, you can’t totally stop window condensation, but you can reduce window condensation. Here are some basic ways to reduce window condensation. You want to do your best at controlling all sources of humidity such as venting all gas burners, dryers to the outdoors. Leave your bath vents, stove vents running for at least a half and hour long after you cook or take a shower.

  • Cracking open a window or door daily to air out your house.
  • Opening a window or running exhaust fans longer in the kitchen, bathroom, and laundry room.
  • Opening drapes and blinds, allowing air to circulate against windows.
  • Turning off any humidifying device in your home.
  • Installing and using a dehumidifier.
  • If you live in a northern climate, the above as well as the following points may be relevant.
  • Adding storm windows or replacing existing single-pane windows with insulated windows.
  • Keeping plants in a sunroom, or in rooms that are infrequently used during extreme cold weather.
  • Adding waterproof protection to basement floors and walls.
  • Removing radiator pans until sweating has been eliminated.
  • Making sure that open-faced gas heaters are connected to a chimney and using them as little as possible.


  1. Wow! Thank you for this information about window condensation! I didn’t realize how much our everyday lifestyles create so much moisture in the air. I’ll have my husband look into ways to reduce our air quality and install a bathroom vent.

    Thank you!

  2. I’m pleased my article on window condensation helped you. Just be sure to run your bath vent for a half and hour longer than usual to sweep up any and all moisture in the bathroom after a shower. Also, if you’ve a kitchen stove vent, run it for the same amount of time after you’ve finished cooking. Be sure to read about window seal failure to be sure that isn’t the problem.

  3. Just wanted to say thank you for this post. I was having a problem with window condensation on my bathroom windows and it was bothering the heck out of me! I did what you suggested and ran the bathroom exhaust vent for 30 mins long after I’d taken a shower. It considerably reduced the condensation problem I was having.

    Happy holidays,

  4. I have the same problem with window condensation. Mostly in the kitchen. Is there any window condensation solution you could give for the kitchen area?

  5. Hello Tim, if you could give me some more information about your kitchen that would be more helpful than having to generalize your situation. For example, are there any kitchen stove vents, plants around the window sills, how old or new is your home, square footage of the kitchen. Do you have a kitchen stove exhaust vent? If so, do you leave it running while cooking and for about 30 minutes after cooking? Are you kitchen exhaust vents clean?

    If you can provide some more information from the above stated, I’ll do my best to provide you with a window condensation solution.

    Thanks again!

  6. Hello John, I’m glad to be of help! If the problem persists, you might want to look into having and electrical contractor install a better bathroom exhaust vent.

  7. Informative article. So what’s the best bathroom exhaust
    vent on the market today? Can you recommend any?

  8. Shelda David says

    Thank you so much for posting this article Mike. My husband
    and I live in Texas and have been in our brand new built home for
    about 3 months. Today we awaken to all of our windows frozen with
    ice and all I could think about that this was going to cost some
    $$$. Living in Texas seeing anything that resembles snow is not
    comforting let alone it being inside your own home. Thank

  9. Mike,

    While I agree with what you have said for the most part, thermal windows are also a viable replacement option that is very cost efficient too.

  10. Great article, I found it very informative. Thank you for the tips at the end especially . I have one particular window that never seems to dry out no matter what the temp any ideas?

  11. Have you tried running a dehumidifier? Is this in the bathroom, kitchen, laundry area? If the latter, maybe your vents are underpowered.

  12. No problem Shelda. I’m glad this article has helped you in some way. Any updates since you last commented here? Has the window problems persisted?