VELUX invented the roof window more than 60 years ago. No other manufacturer has that much experience in this field. Thus, the VELUX roof window is a high quality product. In spite of this, water may still condense on the surface of VELUX windows. This is a natural phenomenon.
WHAT IS CONDENSATION?
Condensation is the humid, foggy precipitation of water on objects such as bottles, mirrors, tiles, or windowpanes. It is formed when humid hot air meets a cold surface. Hot air can bind significantly more water than cold air. If hot air cools off (e.g. on a windowpane), the superfluous water contained in the air condenses on the object.
CONDENSATION ON WINDOWS
Windows are always the coldest surfaces in the room. Therefore, condensation forms on panes first. There is no such thing as a window with the same surface temperature as a brick wall. To that end, several thermo panes would have to be built in the same sash - a construction, which is not feasible.
Due to their position, roof windows are particularly exposed to snow, hail, rain, and storm. Thus, they are cooled off more than vertical windows, and again - condensation will be formed on the roof window before anywhere else.