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Old 12-21-2009, 11:25 PM   #1
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Windows sweating on the inside

I wasn't sure if this fits in here or not but I'll give it a try. I live in an old farm house (50-75 yrs old) with rough cut 2X4 walls. Approximately 6-8 years ago, I pulled all the siding off, put in some windows, moved some, etc, etc.. The walls were covered with 1" pine boards throughout the house originally. Some did need to be replaced and they were as needed. When I put everything back together, I put 1" styrofoam on the exterior walls and then my siding. For some time now, I live in Maine, we have been having quite a time with the bottom 1-2" of most of our windows building condensation during the winter. At times, it gets so bad that it builds and drops down onto the trim and pools (at times- not sure if there is a pattern here or not). It has been quite cold lately but I'm at a loss why this is happening. I've been told that the house it too tight. Is this a possibility? I'm looking for ideas and solutions. Thanks,

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Old 12-22-2009, 12:29 AM   #2
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Our house was built in 1995 and we have the same problem. The house does not have house wrap, but I've heard the same explanation - the house is too tight. Our builder told us to run the furnace fan all winter to keep moisture from condensing on the windows. We did that, but moisture still condensed. We are now in the process of replacing most of the window sashes because they are rotting. Not a cheap project.

In our case, only the glider / slider windows are rotting. The casement windows are still ok. Moisture condenses on cool surfaces, so my guess is that these windows are more leaky than the casements. Interestingly, the stationary half of the sliders are worse than the operating half. Not sure why that is.

We just replaced our furnace and central air. The contractor said that an air exchanger / dehumidifier is needed to eliminate the condensation problem on the windows. That solution fits the theory that the house is too tight.

Until you "solve" the problem - maintain your window sashes. Try to keep them dry. Refinish them each spring so they don't rot - new paint or sealant. If your windows are sealed (natural wood), consider an exterior sealant.
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Old 12-22-2009, 06:04 AM   #3
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Condensation on the inside of high efficiency glass is an indication of high humidity inside the house. Sources include, lots of house plants, no fan in showers, cooking, tight house. In the winter, 50% is high. Do you have a humidity gauge?? It sounds like you tightened up the house well when you remodeled. What kind of insulation in the walls, vapor barrier?? You may need a whole house air exchanger.
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Old 12-22-2009, 08:13 AM   #4
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We just had a post and a long thread, just a few days ago, on that; read that for a full explanation of why humidity condenses on cold windows. But the short answer is that there is too much moisture in the air and/or the ventilation insufficient to dissipate it. This brings up the question of the temperature at the window...
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Old 12-22-2009, 09:37 AM   #5
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I've got an old cottage with single glazed windows, which, living in a damp climate are always wet. It's no problem, the wife goes round them with a J cloth all day. It's a cheap type of dehumidifier.
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Old 12-22-2009, 01:21 PM   #6
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Here is the thread Ccarlisle was talking about. Very informative.

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