Condensation /black mould around window returns

carly

Background. :    Been in this house 40 years, since it was built and never had a problem before.   The lounge bow window is approx 5years old. Upvc double glazed, facing roughly but not due North  in a wall with cavity wall insulation fitted in the 80s.   Now unsurprisingly, in a cold winter there has sometimes been  very little condensation on the glass panels sometimes, in the morning, easily dried and never spreading to the wall surface.     Recently though  I have noticed a small (teaspoon sized) pool on water on the window cill once or twice. In the corner where the window frame and wall meet. Also the vertical reveal seems to be damp with faint traces of condensation/mould.  I can’t think of any changes to the way we use the room nor any reason for an increase in humidity in the room.   Can anyone throw any light on why this might be happening. There doesn’t seem to be any gaps in the sealant around the external window frame outside.  I’d like to prevent the problem getting any worse.

donnablossomm

Your sealant may not have gaps in it, but it could be worn down? If the window is starting to get older then the sealant becomes less effective - either that or the window/house has warped and the gap between the frame and wall has increased