Why does condensation occur on the inside of my windows?
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This is a common problem in cold climates during the winter, when windows can be some of the coolest surfaces in the home. Condensation will typically appear there before it appears on other surfaces. Condensation is less likely to occur on interior walls, because they are typically warmer than "dew point."
The "dew point" is the temperature at which condensation will occur for a given humidity level.
To reduce or eliminate excessive condensation, the humidity level must be decreased and/or the ventilation increased
You can removed the amount of moisture in the air of your home by using a household dehumidifier or increasing the amount of ventilation.
Before investing in a dehumidifier or an HRV, check the structure for other possible moisture sources. Ensure the appropriate insulation and moisture barriers are installed in the attic, basement or crawlspace. Check for seepage in the basement.
The Facts About Condensation
Reduce and Control Household Humidity: It should be pointed out that a little fogging or frosting that comes and goes on the lower corners of our windows is nothing to be concerned about. Condensation that blocks the whole window with fog or frost, though, presents more of a problem.