Would one of these things be suitable or overkill?
Our walls never got wet, just mould used to grown in the corners, and windows used to be damp in the morning. Neither things happen now.
The other thing they do if nothing else is keep the air in your house fresh without having to open windows. I think even if a future house isnt damp I would get one, just so that air circulates around.
You need to check that your loft space is the right type though.