Windows and Humidity
Condensation is not caused by window defects. REGIONAL windows are among the top-of-the-line products on the market in that regard. However, condensation is unavoidable when the humidity level inside your house is too high. The dew point (when condensation starts to appear on your windows) depends on the ratio between the humidity level inside your house and the outside temperature. If your house is not equipped with an air exchanger and you notice condensation, you will need to lower the humidity level inside your house as the outside temperature gets colder.
The following chart shows the recommended maximum humidity level inside your house to avoid condensation problems, according to outside temperature.