frozen condensation on storm windows

gincybDecember 4, 2005

We've just moved into a 'new' old house (1790) in VT. My SO is concerned about condensation freezing and building up ice on the inside of the storms (Do I have to mention that the regular windows leak severely?)

We plan to install some sort of new window protection next year, but he is concerned with possible damage this winter. Anyone have any experience with ice buildup on aluminum storm windows? These are probably 50 years old.

Thanks for any info,


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The only way to stop the ice is by stopping the leaking of warm air from inside. The 3M window plastic may help if it's not to bad. You can also try and some how install a weather stripping around your windows to stop air infiltration. It's hard to diagnose with out seeing. Just a couple quick ideas to start with.
Good Luck!

    Bookmark   December 4, 2005 at 5:07PM
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The 3M plastic works well. I used the shrink wrap stuff. I put it up with the double sided tape and shrank it with the hair dryer. As long as it's not puntured I was fine. Besides as bad as it is, the house made it this long and will probably make it another winter.
Look at the bright side - if the windows are frozen shut nobody can break in.

    Bookmark   December 4, 2005 at 7:11PM
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My 1907 house has triple-track aluminum storms likely the same age as yours, and I've never had ice build-up here in Ohio...but I will tell you that they are next to worthless as storms! My front window is a large central one, with two narrower ones on either side--the big one has no storm as it is never opened, but the other ones do have them. I put plastic over the whole thing because the air infiltration is terrible--around the aluminum storms!
The plastic film is very good, although the double-sided tape isn't so great--it can come loose no matter how clean your surfaces are--I supplement it with duct-tape.
Keeping the plastic intact is vital, which is difficult this year because I have a nine-month old siamese kitten who just loves sitting in window sills, and will go through the plastic like butter if I don't watch her!
I am currently planning on building my own wooden storms, so I will not have this problem next year.

    Bookmark   December 4, 2005 at 7:45PM
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The frozen condensation is pretty common, especially with leaky aluminum storms. But the problem is not just the storms, your primaries are also probably "leaking" warm, moist air into the space between the two windows.

The cure is better storm windows, better fitting storms and primaries which are well-tuned up all arouond.

This does NOT mean you have to replace your windows. You might want to consider better storms, however.

It's a project that can wait for spring. The only possible damage (other than the emotional toll of living with opaque windows) is that when it warms up the condensation can melt and drip down onto the window sill, which can harm the wood, particularly if it's a little thin in the paint department. You can try drying it up on warm days, but it will re-occur.

I live in northern NY along the VT line; you know you're truly in the depths of winter when *both* your storms and your primaries are frozen over.

It can be improved, with homeowner-level work in warm weather. It's too cold now!


PS: One other thing, make sure your storms are properly closed, with the upper one on the outer track, lower one inside and correctly mated at the meeting rail.

    Bookmark   December 5, 2005 at 2:47AM
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Old storm windows were made to leak. They had a little flap that could be raised to allow air in. The primary problem with storms getting frosted is not from them leaking, it is from leaks of warm moist inside air into the cavity between the two panes. as Window_Guy and subsequent posters have indicated, if you stop leaks from your inside windows, you won't have a problem with icing storm windows. If you don't stop those leaks, it doesn't how airtight the storm windows are, you will always have frost.

    Bookmark   December 5, 2005 at 6:48AM
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I've found that if I completely close off a window (close shutters or draw drapes) that there will be condensation in the morning. Therefore, I make sure to leave a little air movement going on. I don't know what the energy experts would say, but I don't see any other way. I have Andersen thermopane sash and casements.


    Bookmark   December 5, 2005 at 6:47PM
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Heat always travels to cold and wet always travels to dry - (unless acted on by an outside force). Your windows are a prime example of that principle.

In the winter, the outside air is cold and dry. Cold air does not hold moisture very well and no matter how dry your home may feel to you, it is still holding more moisture than is the air outside. That warm and moist inside air wants very badly to equalize with the cool dry outside air, so it is looking for a way to escape from your home.

In the middle of summer, pull a can of something cold and frosty out of the refrigerator and notice how quickly the can becomes wet on the outside. This is condensation caused by the contact between the warm, moist summer air and the cold can. The surface of the can is below the dew point. Trying to stop moisture from forming on the can is impossible because it is some very basic physical laws at work.

Unfortunately, those same physical laws are affecting your windows in the winter when you get moisture forming on the surface of the glass. Your leaky inside windows are like an open invitation for your nice warm inside air to go outside...and in the process, it is drawing lots of nice warm, moist air to the storm windows. The warm air is contacting the storms and, like the can out of the refrigerator, the glass surface is below the dew point of the air inside your home...thus, condensation on the glass surface.

With a single pane window, when the temperature is 0 degrees outside (F), the face of the glass inside is only about 16 degrees. At 16 degrees, it doesn't take much moisture to cause condensation on the surface of the glass. BTW, the numbers I am using are center-of-glass measurements - edge readings will be lower by several degrees.

If you add a "tight" storm window, then the surface of the inside of the inside window may be about 40 degrees or so, when the outside temp is zero, but that outside storm is still going to be well below freezing.

At 40 degrees, for example, it takes only about 6-1/2 grams per square meter of moisture in the air to reach the 100% RH level or dew point temperature - which is pretty close to the temperature of your windows. At that 6-1/2 grams of water per cubic meter an RH reading of only 30% at 75 degrees is sufficient to have moisture on your inside windows - at that moisture level.

At 32 degrees it obviously takes even less moisture to reach 100% RH which will cause condensation and subsequently frost or ice on the storms.

Ultimately, there are two things you can do to help prevent moisture from gathering on your windows first, you can attempt to increase the temperature of the windows to a mark above the dew point, and second, you can attempt to block the warm, moist air from reaching the glass.

In order to raise the dew point of the windows themselves, you will have to assist your homeÂs heating system by using small fans or, even better, small forced air heaters, close to, and directly facing the glass. I suspect this is not a practical solution, except for maybe the very worst offenders. This "solution" should warm the inside glass enough to avoid moisture build-up, but at an obvious cost in your energy usage, but it may not do a thing for the water and ice build-up on the storm windows  only on the inside glass.

As Guy suggested, the plastic window covering is probably the best possible "solution" for your situation. The plastic film will help to keep inside moisture away from the windows.

Also, as Carol suggested, keeping blinds and curtains open will help a great deal control inside condensation, but that won't do much for icing-up storms, unfortunately.

    Bookmark   December 5, 2005 at 7:19PM
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Thanks for all your help. I think we'll put in interior storms next year. Seems like the way to go. We had plastic put over the inside of a couple of windows where the storms were missing, and they don't produce any condensation at all.


    Bookmark   December 7, 2005 at 12:18PM
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What role does a woodstove and the dry heat play on the similiar situations as noted above? I have lots of condensation and will attempt to tighten the air flow as I recently bought new replacement triple track storm windows which are not properly installed.
I have one window with no condensation in the same room!

    Bookmark   December 8, 2010 at 8:24AM
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I have new construction with Anderson double-pane windows that are tight. Plus double-cell insulated shades. On the coldest mornings (less that +10) we were getting some condensation and even frost on the insides of the windows, between the inside window surface and the shade. I think that is because the shades are so effective.

Anyway, we added triple glazing this summer, in the form of tight-fit Humphrey storm windows. Now as the winter proceeds, I'm discovering that the condensation (quite a bit) is occuring on the inside surface of the storm window.

My interpretation of all this is that without more air leakage, this tight system will cause condensation on one surface or the other, that the only prevention would be to allow more leakage to ventilate it.

    Bookmark   December 12, 2010 at 9:17AM
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