My husband and I are both involved with interiors, and his comment is that the gap between the windows and the shutters, plus the fact that they are just slats would not give you condensation problems. However, from the design point of view, make sure you are happy with the fact that if in situ constantly (ie not folded to the sides) you are happy with the feeling of not being able to see out. You may of course have space to fold them back and intend to do so. I would also recommend that you look/consider from outside too, at the proposed 'lines' that will be there once fitted, because you will always then be looking at the lines of the windows AND the lines of the shutter panels, and sometimes this can look very 'busy' and cluttered