No, condensation on windows is not the fault of the window. However, by replacing drafty windows and doors, or installing a new roof or siding, you are reducing air flow in your home and making it tighter. Tighter homes actually retain more humidity. To reduce condensation, humidity must be controlled and air movement must be generated. As the exterior temperature drops, the humidity level needs to decrease if condensation is to be controlled.
New materials and techniques in weather stripping, insulation, vapor barriers, etc., which are intended to keep out cold air, also lock moisture inside. As a result, moisture created by bathrooms, kitchens, laundries, and occupants no longer flows to the outside unless mechanically ventilated.
No, windows do not make condensation. Generally, condensation on insulated glass windows is the result of excess humidity. Window glass provides a cold surface on which humidity can visibly condense. The fog on your windows is a form of condensation – just like the water that forms on the outside of a glass of iced tea in the summer and on the bathroom mirrors and walls after a hot shower. When warm, moist air comes into contact with the cooler glass surfaces, the moisture condenses.
Condensation is not necessarily an indication that your windows are bad. Condensation on windows depends upon a number of factors: type of glazing, frame and sash materials, glazing spacer material, depth of glazing into sash, and other construction details.