How to Stop Condensation on Inside of Windows

You’ve probably noticed that when it’s cold outdoors, you often get frost or condensation on your windows indoors. Over time, this problem can compound to the point where water accumulates on the inside of your glass and eventually begins to drip. This dripping becomes an issue as it can cause water stains and even permanent damage to your sills and flooring. If you’re really lucky, and you have a thirsty cat, he or she will let you know how bad your window condensation problem is by licking the accumulating moisture off the glass. Yuck! Let’s take a look on how to combat this problem once and for all.

Condensation on inside of windows
What causes water condensation on your panes and how do you stop it? We know that when you heat your house, you warm the air contained inside. This warmer air holds more moisture than cooler air. When the warm air meets a cold surface, the water molecules from the air get less “excited” and settle down. As they settle,  they group together and form visible condensation. And just like a cloud, the accumulating moisture mass becomes lighter than air and gets pulled down by gravity in the form of rain droplets (in simple terms!). In this case, you’ve created water droplets inside your home. This isn’t a good thing indoors, unless you’re washing dishes or taking a shower! So, we need to take a look at how to control this warmer air and also how to remove the colder window surfaces from the equation.

How to stop condensation on windows
This article talks about some ways to help your wet window problem. Solutions range from no-cost to thousand of dollars – can you say “new windows?” Here, we’ll focus on remedies that don’t break the bank. Some tips may not apply to your specific situation, but should be worth considering.

Solution #1 (Good)

Rain-X Glass Anti-Fog This long-time, trusted product has worked to stop car windows and bathroom mirrors from fogging up. The insides of your home windows where heavy fogging occurs aren’t much different. Simply wipe on window glass surfaces until the solution disappears. Reapply as needed. May not work as well in extreme cold or humid conditions. Amazon sells for cheap – get 2-3 bottles depending on how many windows you have!

Solution #2 (Better)

Window Film Kit to help with condensation When applied to the inside of your windows this 100% see-through film can keep glass surfaces free of condensation (it blocks warmer/humid indoor air from reaching the cold glass and fogging/condensing). What’s more is the film obviously helps keep your house warmer too in addition to aiding condensation build-up. This stuff goes on perfectly clear. Check out the reviews at Amazon. This product is also eligible for a tax credit since it helps to weatherize your home. You might also try monitoring the humidity and dew-point levels in your house with a Thermo-Hygrometer – a great little gadget that tells you the current humidity level indoors.

Solution #3 (Best)

A dehumidifier placed in the room will stop window condensation
If you really want to eliminate your problem, place a dehumidifier in the room (preferably by the offending windows). This portable unit will remove moisture from the air to the point that it won’t “stick” to your windows any more (as described above). These guys are quiet, energy efficient and will last season after season – they are well worth the investment.
Here’s a very popular model at

For a little less money and non-electric option you can place a smaller,
renewable unit that takes water out of the air without being plugged in. These
are designed for smaller spaces like a bathroom, but placing one or two under a
troublesome window will certainly cut down on the moisture around your cold
glass there. These are great, if you’re going out for the day and want something
working while you’re gone. This is the one to get.

More low-cost ways to beat window condensation
Window condensation is most likely to occur during colder winter (or spring and autumn) months and usually in the morning hours when temperatures are cooler. If your window fog is temporary, such as only first thing the morning or during a large gathering of people, your fix is usually just to wait it out, unless the condensation starts “leaking” off the glass.

The best way to disrupt the warm, moist air from moving to and sticking to your cool windows is to disrupt stale air and get it moving. If it’s not too cold outdoors, opening the house up (cracking doors or windows slightly) can be the solution. This allows the colder, drier air from outside to mix with the warmer air around your windows. In older homes that aren’t sealed as well, this happens already, as cooler air from the outside sneaks in around windows. If you’re getting window condensation, it just means your house is sealed relatively well and energy efficient. You may even have newer or double-glazed glass on some of your windows lending to thi. Many times though, it’s best to just turn the house fan on in your forced-air system to move the air around. If you’re already running a furnace/heater though, and the blower is running, flip your switch to continuously run the fan. That means, air will be moving even when heat isn’t coming out. Be sure to have curtains open so the circulating air can move around and help dry up the window condensation faster. If you have a longer-term window condensation problem, then you may need to add a dehumidifier to your HVAC system or get a less expensive portable one.

Before getting a dehumidifier though, let’s look at how to decrease the overall humidity in your home. It’s obvious that people’s bodies/breathing, showers, baths and cooking create moisture in your home. To cut down some of these water sources, be sure to run the exhaust fan in kitchens and baths. Here are some other causes of moisture in your home that you may want to consider as you reduce your home’s relative humidity:

  • Houseplants: the more you have, the more humidity
  • Dryer vent: make sure it goes outdoors and is sealed well
  • Wet or damp laundry: do not hang to dry indoors
  • Fish tanks: cover up aquariums to reduce humidity
  • Stop breathing: humans expel a lot of moisture while breathing…okay, maybe you shouldn’t use this tactic!
  • Basement floors/walls: seal these surfaces by painting or coating with concrete sealer to help keep moisture out and raising your relative humidity in your house
  • Rain: inspect that your gutters and drains are all diverting water away from the house; i.e., keep water away from your foundation

Once we can get air circulating and reduce the humidity levels, the next thing to look at is keeping the surface of those windows as warm as possible to further reduce the formation of condensation. The obvious one, although expensive, is to install double or dual-glazed windows. You can also add storm windows to the outside. Both of these solutions help keep inside glass surfaces warm. If installing new windows, be sure there is good insulation in your window framing or the walls around where they are. The more cold air coming from around them, the colder your new, “warm” windows can become, which leads to water condensing on the glass or sash. To prioritize when considering budget, try installing storm windows just on the north side (coolest side) of the house. Or, if you live in a windy climate install these on the opposite side of the house from where the wind comes from.


  1. ronald says;
    07 Nov 2010 - 4:18

    This had some good information.

  2. XXdragon slayer364589 says;
    27 Nov 2010 - 17:15

    This helped so so so so so much I have ecessive condensation on my pella windows. I have not done any of the procedures to help reduce the condensation on the windows but i am glad the problem is not just mine and hopefull that some of these techniques will.

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