I have a remodeled two story house with basement in central Iowa, which was originally built in 1896. About four years ago a complete remodel was completed with none of the original house remaining including the basement and foundation. Parts of the house that was an addition about twenty-five years ago did remain. The house got all new Pella double pain windows with wood interior. During the winter, condensation develops on the windows on the bottom inch or two of the glass. I have tried to a dehumidifier and fans to keep the windows dry but it does not work.
What is causing this and how do I prevent it?
Replies
Actually, some condensation is "normal" in your area, though 2 inches is maybe a bit much, especially if you're keeping the rooms warm, have fans circulating the air, and don't have heavy curtains.
Condensation occurs because the air in the immediate vicinity of the windows is colder than the dew point of the inside air. So basically you need to either raise the temperature or lower the dew point.
It would help to have measured the humidity % in the house during the winter. Generally it should stay below 40% through most of the heating season, and should drop as the temperature drops -- roughly 20% at 0F. If your humidity is staying above these levels then I would expect that there is some moisture source in the house.
A most common moisture source in a "new" house is the new lumber and drywall. It generally takes 6-12 months for these to dry to levels sufficiently close to normal to not affect interior humidity.
If humidity levels aren't the problem then I would suspect that there is significant air infiltration around the outside of the windows. Especially in a retrofit situation, installers often aren't very careful about sealing between the window rough opening and the outer window frame. An enormous amount of air can leak through this area, and the window trim tends to blow a lot of it across the window itself. When this cold air mixes with moist inside air then condensation results. Removing the window trim and foaming this area with low-expansion foam can make a dramatic difference.