In one of the bedrooms in my house (1930s), there is a sunken alcove where an old window used to be, the internal sill is still there. Whoever bricked up the window used bricks much thinner than the rest of the wall, resulting in the 11cm deep internal alcove.
Because it's so thin, the wall here gets really cold resulting in condensation ruining the paintwork. I'm planning on blocking up the alcove with some stud work, but I was wondering what kind of insulation I should use? Should I be concerned about the condensation, or is that likely to go away once the insulation and stud work is done? Is there a better way to fill the alcove?