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Sweating windows

What would cause my windows and doors to sweat when it gets cold out if the indoor humidity is low? They are new windows and doors. The windows freeze shut when it gets about 10 degrees and the door handles freeze as well. I don't know the exact indoor humidity, but I can tell you it is low by how dry my skin and nose are in the morning. I keep the indoor temp about 65 to 70. Can anyone explain the problem and how to fix?

Asked by ben g
Posted Sun, 02/16/2014 - 10:39
Edited Sun, 02/16/2014 - 14:06

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5 Answers

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1.
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Ben,
There are only two ways to reduce condensation on your windows and doors: either lower your indoor humidity level or install better windows and doors. If your doors and windows are cold, that's where condensation occurs. Windows can be warmed up by adding an exterior storm panel. If your doors are poorly insulated, you could install a better quality door with more insulation or better weatherstripping.

The only way to determine your indoor humidity level is to measure it with a hygrometer. You can buy one at Radio Shack.

Common causes for high indoor humidity include damp basements or damp crawl spaces. If you are sure that your basement is dry, you can lower the indoor humidity during the winter by increasing your ventilation rate -- for example, by running your bath exhaust fan for 24 hours a day until the situation improves.

Answered by Martin Holladay, GBA Advisor
Posted Sun, 02/16/2014 - 15:07
Edited Sun, 02/16/2014 - 15:08.

2.
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Hi Ben,

You mention new windows, how new are they? It isn't uncommon for people to experience window condensation after installing new windows because the new windows are a lot tighter than the original windows that they replaced resulting in higher indoor humidity levels.

I am assuming that you have dual pane windows, do they have a LowE coating and/or argon (or other) gas fill? Who is the manufacturer?

10°F really isn't very cold, so mentioning that your windows freeze at that temperature does suggest that your indoor moisture level is high but also that you may have some air leakage that cools the interior glass/frame enough to result in frost or ice on the windows.

Do you have blinds/shades/curtains that you keep closed in front of the windows? That is a very common reason for condensation and freezing when outdoor temps drop below freezing as well.

Answered by Greg Smith
Posted Mon, 02/17/2014 - 15:15
Edited Mon, 02/17/2014 - 15:16.

3.
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Most of the windows are about 2 years old. One of them and the patio door is about 5 years old. They are Marvin Integritys, double hung, dual pane, low e. I don't have blinds on most of them. They freeze up around the seals and at the sill. Both entry doors also get a lot of ice build up around them and in the knobs. It already feels way to dry in my house according to the way my body feels in the morning, but its also really annoying that my windows freeze up. The old windows were even worse. They would actually get a measurable layer of ice on them and they all smelled like mold.

Answered by ben g
Posted Tue, 02/18/2014 - 07:36

4.
Helpful? 0

Ben,
You can't fight the laws of physics. If you have condensation, you must either lower the indoor humidity level, or warm up those cold surfaces by installing exterior storm windows or swapping the existing windows for windows with a lower U-factor (higher R-value).

Most homeowners would conclude that the easiest path is to lower the indoor humidity level. But it's your choice.

For more information on this topic, see Rating Windows for Condensation Resistance.

Answered by Martin Holladay, GBA Advisor
Posted Tue, 02/18/2014 - 10:56
Edited Tue, 02/18/2014 - 11:25.

5.
Helpful? 0

A tight low-E exterior storm window over a ~U0.30-0.35 is window will bring it's performance to the low to mid-0.2s, and will raise the min temp at the interior pane a handful of degrees, and for FAR less money than a U-0.22-0.25 replacement window. Harvey TruChannel is the tightest in the biz, and has a low-E glazing option. The Larson low-E storms sold through box stores are pretty good too, if you upgrade to "silver" or "gold" series.

But measure your indoor humidity- buy few $10 AcuRites and leave them in a few rooms- you may be surprised how high your indoor humidity really is. If it's bumping on 40% RH @ 68F during the coldest weather it's worth taking measures to bring that humidity down to sub-35% to limit the springtime mold risk inside your walls, as well as the window condensation.

Answered by Dana Dorsett
Posted Tue, 02/18/2014 - 12:06

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