Why do our windows collect condensation?
In a nutshell, the cause is excess humidity indoors when it is cold outside. Your windows are not defective, but they are not the kind of super-high-performance windows that would be warm enough not to attract condensation. You should investigate sources of moisture indoors. Usually houses are dry in the winter, not wet, so this is a bit unusual. Do you use a humidifier? If so, turn it down.