Will it have a flat roof you can climb on to stare in through their upstairs windows? Will it have a velux so you can spy on them from upstairs when they're cooking? Will it be on the opposite side of the house so it has no impact on you whatsoever?
Think how it will impact you once in place. Sadly a complaint about the disruption during build isn't valid, but once it's finished, will it affect you at all? If not, you don't need to do anything. If it will, consider how. Overlooking, loss of privacy etc and write to the planning officer to say how it will affect you.