Air vent not stopping mould

[bobbydave]

I bought a new house 3.5 years ago in Ireland. We had a small 4th bedroom which we knocked to put in a full stairs to an already converted attic (there was a pull down stairs in another area that we closed up).

 

Last year, i noticed we were getting mould over 4th bedroom window inside on the ceiling which spread like wildflower. It then started travelling up the new stairs ceiling. 

We had someone put in  4 vent tiles earlier this year.  The issue disappeared. 

 

But now its back but not under the window this time. It is travelling up the new stairs  ceiling again and making its way all the way and going back down the other side of the roof.

 

Surely, I dont need more vent tiles?  (4 vent tiles + labour = 600 euro).

 

Any ideas to rid this once and for all?

Edited Wednesday at 13:23 by bobbydave
typo

[JohnMo]

Air vents are ok when the wind blows, but pretty useless on there own.

 

What fans do you have, and how do they operate?

Do windows have trickle vents?

How was your roof insulated, what and where are these vents actually ventilating?

 

Basics are

You need to establish cross ventilation, so feed in to house from dry rooms and out via wet rooms. The ideal is this all happens automatically and only when needed.

[bobbydave]

Apologies, we had vent tiles put on the roof (i had said air vents, i mean vent tiles).

 

We have an extractor fan for the ensuite shower and the guy who put in the vent tiles ensured me that this is leading to the back and operating correctly.

 

Windows have trickle vents and above the window is now fixed.

I'll attach a video 

[bobbydave]

any one any idea what to do?

[Roundtuit]

Condensation occurs where warm humid air hits a cold surface.  I'd be looking at upgrading the insulation.