Would you agree that if there is condensation on the outside of the internal pane of a double-glazed window that it was faulty? I happened to mention this to a friend and our discussion got quite heated! My house is fully double glazed and I have never experienced heat-loss or condensation. I would worry if I did. She says it depends on certain conditions like humidity, outside temperature etc. which she blames for her having condensation on her windows. I always thought that if you have well-fitted double glazing you should never get condensation, regardless of these factors. There's no point in having it if it doesn't work! If it's keeping the cold out and the warmth in, there shouldn't be any condensation?

Thoughts, please?

What a confusing way to put it. Do you mean between the two panes of glass or on the inside of the window where you can feel and presumably wipe it off?

If the former, then the unit is faulty/has failed. If the later, then no condensation can form depending on ventilation and the temperature of the room in question.

No. Double glazing insulates but it's not a perfect insulator. The inner pane can get colder and if the inside of the house has high humidity such as in a bathroom or kitchen then condensation will form.

Sorry. Yes, the inside of the window.

By this I take you are meaning the 'room side' of the window, i.e. not in between the panes of glass? This can happen from time to time if the glass gets cold enough and the room is humid enough.


In theory, but as above, it's all relative and unless you have super space station triple glazing in triplicate with extra wooly bits round the edges there's no guarantee that there will never be any condensation.

Was there anything right by the window blocking or slowing airflow?

Yes, like nice thick thermally insulated curtains that are doing what they are designed to do.

If it's between the panes of glass it is faulty, as they are supposed to be sealed and air tight