Hi all, appreciate some advice.. We have a slight damp issue which appears in cold weather, in the first floor bedroom next to the chimney breast. Mainly on the ceiling rather than the breast itself. The chimney has been plaster boarded around it throughout the house. It has had a gas fire installed on the ground floor (see internal pic). This has a sleeve running up the chimney, where’s it’s got a ventilated cap at the top but there is no other ventilation. I’m planning to put an airbrick on the outside to try and resolve the issue - this would need to be a bit higher up to account for the fire place on the ground floor and conservatory on the outside. My two questions are: 1) would putting an airbrick half way up (see external pic) do the trick? You can almost see the damp on the outside wall of the chimney which starts around half way up. 2) would we need a vent internally, say in the first floor bedroom, too? Cheers!