The curse of condensation & mould

[NoisyBrain]

I'm SO sick of battling the mould caused by condensation in one of our bedrooms and I'm looking for any MN wisdom.

It's northeast-facing, which doesn't help. On winter mornings there is condensation on the ceiling by the window and along the top of the window frame. We don't want to have the heating on permanently, but have tried the following over the last 18 months or so:

New loft insulation
New soffits and guttering
Replacing a broken roof tile and putting in venting tiles
Getting powerful (bloody expensive) extractor fans installed in the kitchen and windowless bathroom, which automatically increase their speed when they detect humidity.

We now have a bone dry loft, which is great, and I have noticed a reduction in mould appearing in the bathroom, but the bastard stuff is still appearing in the bedroom, and it's more widespread😬

The fan suppliers advised against opening windows on cold, damp winter days as they said all that does is let moist air in. So, I wipe off the condensation and run a large dehumidifier for a couple of hours. Mould Magic gets rid of the mould for a week or two, but it's destroying the paintwork and is clearly not a long-term solution.

I've seen white vinegar recommended, does that really work? Any other tips I may be missing? I've tried everything I can find by Googling! TIA.

Is it a single glazed window? It sounds like the window needs replacing or sealed.

You absolutely need to open windows, people in countries across the world do this to combat damp. I'd get an extractor fan fitted in the bedroom, not a humidistat one but one you can turn on and off with an isolated switch or pull cord. Leave it on when the room is empty, when you go out etc. Even on rainy days it extracts damp air. We had one in our old drafty cottage and it fixed the mould problem.

We did similar but it was once we replaced windows (which now must have trickle vents) that it went away (well to the point where we only had to clean a couple of mould spots every few months)

Also if the window has vents, leave them open overnight. If not, consider having them added.

White vinegar is good for cleaning mould but doesn't stop it.

A bigger job is to replace the window/add secondary glazing/add insulated plasterboard to the window wall to help.

Check the windows seals work, hold a flame (candle works) along the edges to check for draughts.

We purchased a large dehumidifier, Igenix brand, was roughly £300 as previously we had one of those little £50 500ml tank ones and it didn’t make a difference.
Not had any mould since, we don’t get condensation on windows or doors. It gets rid of 20 litres a day.

For existing mould we just cleaned with a store bought spray and then repainted with a damp seal paint.

So far 2 years without issues.

It’s an expensive process but worth it.

The fan suppliers advised against opening windows on cold, damp winter days as they said all that does is let moist air in

They're wrong and they don't understand relative humidity.

The air outside will be cold and feel damp because cold air holds less moisture BUT it will have a lower overall water content than warm air inside that is full of moisture from cooking, breathing etc. So you need to open all your windows wide in the morning to allow that warm, moist air out and the cold, but relatively dry, air in instead.

I would ideally have the heating on low all night to warm the walls and windows but if you don't want to do that then you need to have a dehumidifier running all the time, or at least overnight. If you're drying clothes in the house then you absolutely must use a dehumidifier to get rid of the moisture.

How do you dry the cloths that you're using to wipe up the condensation? If you are leaving them out to dry then you're just putting the moisture back in the air. A window vac will be better but if you heat the house properly, ventilate it and remove moisture with a dehumidifier then you may not get any condensation. Ours has gone completely since we started doing those things, having previously had water running down the walls at times!

This is a good video that explains in detail

Wow, didn't expect so many responses so quickly! Thanks all, plenty to try here🙂

The windows are double glazed and were replaced about 8 years ago, but don't have vents. I use kitchen roll to wipe the window frames then bin it. We have some candles so I'll check the seals as suggested - I suspect that they may not be as airtight as we'd like...

Our dehumidifier was about £200 I think - DH bought it. It's a hefty thing with a large tank. I'll try running it for longer, about to lug it upstairs now. We rarely dry washing inside but when we do the dehumidifier goes on until the clothes are barely damp.