Externally mounted extractor fan

[simonski1]

We have a first floor property which we let out in a 1960s brick-walled, concrete floored, double-glazed building. There is a humidity-driven fan in the kitchen and bathroom. During both of the winters which we've let the property (to different tenants), black mould has very suddenly appeared during the particularly cold snap on the outside walls of one of the bedrooms, the lounge and the bathroom, plus the bathroom ceiling. Both sets of tenants have told us that there is water streaming down the walls at times. Clearly this is condensation, and appears because of "life-style", ie bathing, showering, cooking, washing on radiators and breathing in a warm flat which has cold uninsulated walls. The mould appears at the top of the outside wall and the ceiling in the bathroom, and just above the skirting in the lounge and the bedroom - I believe it's above the skirting because it has run down the walls. I think the best solution would be to dry-line all of the outside walls but that's too expensive and fiddly. What I think would be most practical is to introduce a fan into the hallway to "dribble" air movement through the property and put 1 or 2 air vents into each room - currently there is only one in the hallway. Because there already is a grill in the hall ceiling which (presumably) heads through a cavity and appears as an air brick on the side of the building, I would ideally sit a fan instead of this air brick to suck the air through and out of the flat because this is a) less noisy than having a fan in the hallway and b) I can put it on a timer so that the tenants cannot switch it off. Does anyone know of such an externally mounted extractor fan? Thanks.

 

[Zampa]

Electricans may know a bit more..........