1) Heavy condensation on windows is a symptom of moisture damage that occurs throughout your home. Heavy condensation blocks the whole window with fog or frost (in corners is normal), runoff from these can cause staining on woodwork, wallpaper and plaster.
2) Excessive indoor humidity forms when the moisture in wet air (indoors often) is compelled to flow toward and mix with the outside air (often drier) through vapor pressure. It can force excessive indoor humidity through sliding to form “blisters” under the exterior paint.
3) Modern homes actually tend to trap more humidity inside then older homes. This is because of modern builders increasing use of moisture-trapping material (glass, tiles, etc.). These materials along with the application of vapor-seal wall insulation keep moisture inside.
4) Our lifestyles often contribute to the problem. Today, there is more washing, bathing and showering along with more appliances and gas furnaces. Studies show that a family of four can release more than 18 gallons of moisture per week into the household air.