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Condensation on New Windows

590 tim installing window on ladder

Installing new windows does not guarantee that your condensation problems will disappear. PHOTO CREDIT: Kathy Carter

Condensation on New Windows TIPS

  • New windows cause indoor humidity to go UP - SEE BELOW
  • AAMA gold-label windows are best and have least condensation
  • Trace cause of high indoor humidity - could be houseplants or cooking
  • Check humidity with high-quality hygrometer - see below link
  • CLICK HERE to Get Tim's FREE & FUNNY Newsletter!

DEAR TIM: I'm at my wits end. The new replacement windows in our home are fogging up and some have dripping water on the inside pane of glass.

I thought by buying new windows I would eliminate condensation forever. Are the windows defective?

What's happening and what, if anything, can be done to minimize the problem? Pamela S., Gatlinburg, TN

DEAR PAMELA: The condensation on your new windows is very unfortunate.

Multiple Moisture Sources

The source of the problem is not easy to trace and to make matters worse, there can be multiple things that are happening that can contribute to the problem. It's my opinion that you will solve the problem using old-fashioned detective work that employs the process of elimination.

Related Links

Window Condensation is Common

Simple Science of Condensation

Free & Fast BIDS

CLICK HERE to get FREE & FAST BIDS from local window replacement contractors. Ask about AAMA windows. See below.

Water Vapor + Cool Glass = Condensation

Let's start the investigation by reviewing what causes condensation on windows, in crawlspaces, on air conditioning ducts and even in attics. The air inside your home contains moisture. It is invisible water vapor, but it is there.

You and all of the people in your family contribute to this moisture each time you exhale. Try fogging a mirror with your breath and you will see what I mean.

condensation new windows

This is condensation that's turned to frost on new windows. It's a piece of high quality insulated glass in my man cave. The outdoor temperature was minus 6 F and there's NO humidifier in this building! The same frost on nails could be happening in my attic! Copyright 2018 Tim Carter

Sources of Water Vapor

Lots of other things around your home also contribute to the addition of water vapor in the air. Uncovered ground in crawlspaces, indoor plants, laundry hung out to dry, cooking activities, aquariums, humidifiers, etc. all add water vapor to the air.

Add to this the natural humidity that Mother Nature contributes to the air all around us and you can see that humidity is a very common thing.

Warm Air Holds More Water

The amount of humidity in the air can rise and fall depending upon the temperature of the air. Warm or hot air has the ability to hold much more water vapor than cool or cold air.

So the humidity in air is relative. Relative humidity is defined as the percentage of water vapor in a given amount of air at a given temperature.

Dew Point

When this percentage gets to 100 percent, the water vapor, a gas, changes from a gas to a liquid. Meteorologists refer to this complete saturation as the dew point.

Cool Glass

Water is forming on your new windows because one of several things is happening. The temperature of the inner glass surface is at or below the dew point for the amount of humidity in your inside air.

New Windows Cause Humidity To RISE

The humidity of your indoor air is quite possibly much higher now with your new windows because the air leaks around your old windows were eliminated once the new windows were installed. Cold, drier air that leaks into homes from the outdoors lowers the relative humidity indoors.

This is one reason people have static electricity problems in drafty homes during the winter months. Dry air makes it very easy for the static sparks to transfer from your hands to grounded objects.

CLICK HERE to get FREE & FAST BIDS from local window replacement contractors. Ask about AAMA windows. See below.

Test Humidity With Hygrometer

I suggest you purchase a decent hygrometer for under $50.00. This tool will allow you to get accurate readings of indoor humidity.

Start to take daily readings and then look around to see if you have things that add too much water to the air. Make sure crawlspace soil is covered with high-performance vapor retarders.

This is a fantastic high-quality hygrometer. It says Psychrometer on it, but that's the fancy name for hygrometer. CLICK THE IMAGE NOW TO HAVE THIS DELIVERED TO YOUR HOME.

Eliminate Humidity Sources

Minimize the number of indoor plants you might have. Run kitchen exhaust fans if you boil lots of water when you cook. If you have a vent-free fireplace, limit its use as it produces vast amounts of water vapor when it burns natural gas.

Be sure to operate bathroom exhaust fans during bathing activities and pipe this humid air directly to the outdoors.

Blow Air Across Windows

If you discover that your indoor humidity is not too high using your hygrometer, then you can minimize or eliminate the condensation by creating air movement around the windows. Just as blowing air dries say laundry things outdoors, air blowing over the interior glass will act just like the defroster does in your automobile.

Dangers Of Stopping Air Infiltration

Efforts to stop air leakage into homes can create all sorts of secondary effects. One of them is potential increases in indoor relative humidity levels. Indoor air pollution levels can also rise.

Tightly-constructed new homes or older homes where energy-savings measures are employed create situations where little fresh air enters a home to equalize humidity and freshness.

AAMA Windows Have Least Condensation

Not all windows are made to the same standards. Some new windows may use poor-quality parts and poor construction methods that allow the glass temperature of the inner pane of glass to be much cooler than a well-built window. The best windows are those that come with the AAMA Gold Label on the frame.

The cooler pane of glass will show condensation before a warmer pane of glass. This is why an empty drinking glass on a kitchen counter or a piece of glass in a picture frame has no condensation while a window two feet away is fogged up or dripping with water.

CLICK HERE to get FREE & FAST BIDS from local window replacement contractors. Ask about AAMA windows.

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11 Responses to Condensation on New Windows

  1. Im having horrible condensation problems on all windows primarily iny master. The window ledge wood is starting to warp from the condensation and mold is forming between the frames. My house is less than 3 years old. The master seems to be the hottest in the summer and coldest in the winter compared to the rest of the house. What would be the best way to resolve my issue?

  2. Installed a new Pella Thermastar slider for a egress window in the basement. The window is still not trimmed out on the inside because we are still framing, etc. we had two days of rain and we noticed that we had water under the vinyl sill of the window in both lower right and left hand corners. When you ran your finger under the sill in would get wet, but it is not wet enough for the water to drip onto the framing under the sill. We can not figure out what is causing this, a leak, condensation, or what? We are afraid to drywall around the window and finish the room because we can not figure out what is wrong.

  3. Hi Tim,
    Regarding window condensation I recommend you add a warning to readers that they can also have a CO problem due to a faulty house heater causing the condensation on their windows. Properly maintained CO detectors in homes using fossil fuels are essential, but never a fail safe for a root cause analysis of their window condensation

  4. tim
    I think that improperly vented clothes dryers will also raise havoc with sweating windows.
    I installed ceiling fans in every room in my house including the bathrooms. we run the exhaust fan which is vented to the outside and when done bathing, we also turn the ceiling fan on to move the air for an hour or so and voila no more sweaty windows. we also make sure that the firewood we bring in for the fireplace insert is well seasoned as while it is waiting to burned in the holding area, it does not give off humidity.
    our family doctor told us years ago to get rid of the humidifiers because all they were good for was causing upper respitory infections. (colds)

    • Michael, I am surprised your doctor made such a blanket statement. I purchased a humidifier a couple of years ago because we got tired of waking up with dry irritated nasal passages and throats when our forced hot air system was running during the cold winter months. Bringing the room humidity up over 40% definitely made a positive difference for us. I could see excessive humidity being a problem, so there must be a reasonable range.

  5. Tim, Relative humidity is the percentage of moisture in air at a given temperature RELATIVE to the amount of moisture in air at saturation (100% relative humidity) at that temperature. That is why the same amount of moisture will result in a lower relative humidity as the air is heated.

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