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My house has had double glazing for over 10 years although fitted over a period of time. I have had no issues with damp or condensation in the house until about 4 years ago. It started with severe condensation on the windows in my bedroom and the wall below (back of house) last year this spread to two other bedrooms. This year the issue has spread to every room in the house. We have vents fitted in all rooms and have made no building changes recently. What could have happened to make this issue start to appear and how do I fix it. The water is literally streaming off the windows onto the floor. Having a window open or closed makes no difference. I have tried a dehumidifier in the room but this does not seem to be removing much water from the room, the rooms do not seem to be damp. Any ideas ?

Hi Capable Amateur,
This is a tricky one. As you probably know, condensation occurs when warm, moist air is cooled quickly and no longer can 'hold' the moisture. This typically happens when the warm air hits a cold window or wall, and the water vapour in the air condenses on to the cooler surface.

With this in mind, you have either got a lot more warm, moist air in your home in the last 4 years or you have a got more cold surfaces for the moisture to condense on. It could possibly be a combination of the two.

- Have you changed you lifestyle to create more heat and moisture in your home? (possibly more people around showing, boiling the kettle cooking etc)
- Have you checked that the double glazing is still working and has not blown? (if this is where the condensation is really forming).

Please have a look at this project about stopping condensation and this might give you a few more clues!

https://www.diydoctor.org.uk/projects/condensation.htm