Black mould above window

I've just stripped the wallpaper from the bedroom wall. Above the window is a patch of black mould / mildew.
On closer inspection I found there is an airbrick venting the cavity above the window. I suspect that driving rain gets blown into the cavity and has caused the damp.
My thoughts are to put a louvred vent over the airbrick to allow ventilation, but reduce water ingress.
I can then treat the mould and decorate.
Any other ideas?
TIA
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
It may have vented through to the room once...

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I think the air brick will be making the inner wall colder in that area, so condensation is forming and causing the mould to grow. I doubt that it will be water ingress.
You will probably need to get rid of the condensation, open your windows for half an hour each morning or something. Our house grows black mould at the slightest provocation if not well ventilated, usually high up in the corners of rooms with outside walls, but it's just condensation. I periodically attack it with thin bleach.
--
Tim Mitchell

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Thanks for the advice Tim, sounds like the previous owners kept the windows closed! We have some smaller patches in wardrobe corners etc.
Marc
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.